energetic particles in magnetic confinement systems · energetic particles in magnetic confinement...

PROGRAMME

ABSTRACTS

Princeton, USA 5 – 8 September

2017

15th IAEA Technical Meeting on

Energetic Particles in Magnetic Confinement Systems

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15th IAEA Technical Meeting on

Energetic Particles in Magnetic Confinement Systems

5 - 8 September, 2017

Princeton, NJ, USA

IAEA Scientific Secretary

S. M. Gonzalez de Vicente

International Atomic Energy Agency

Vienna International Centre,

Wagramer Straße 5

PO Box 100, A-1400 Vienna, Austria

NAPC Physics Section

Tel: +43-1-2600-21753, Fax: +43-1-26007

E-mail: [email protected]

International Programme Advisory Committee

Chair: E. Frederickson (USA)

M. Podestà (USA), H. Berk (USA), A. Fasoli (Switzerland), T. Fulop (Sweden),

W. Heidbrink (USA), Y. Kolesnichenko (Ukraine), P. Lauber (Germany), S. Pinches

(ITER), S. Sharapov (UK), K. Shinohara (Japan), Y. Todo (Japan), G. Vlad (Italy),

C. Wei (China)

Meeting Website:

https://nucleus.iaea.org/sites/fusionportal/Pages/Energetic%20Particles%2015/General-Info.aspx

mailto:[email protected]

Topics

I. Alpha particles physics;

II. Transport of energetic particles;

III. Effects of energetic particles in magnetic confinement fusion

devices;

IV. Collective phenomena: Alfvén eigenmodes, energetic particle

modes and others;

V. Runaway electrons and disruptions;

VI. Diagnostics for energetic particles.

Tuesday, 5 September, 2017

8:45-9:10 Welcome and Opening Address

Podestà M., Gonzalez de Vicente S.M.

Session 1: TAE Fast Ion Transport

Chair: E. Fredrickson

9:10-9:50 I-1: Todo Y.

Global transport of energetic particles due to the synchronization of multiple

Alfvén eigenmodes brings about the profile resiliency

9:50-10:15 O-1: Lin D.J.

Fast-ion profiles in discharges with Alfvén eigenmode activity

10:15-10:40 O-2: Van Zeeland M.A.

Alfvén Eigenmodes and Fast Ion Transport in Negative Triangularity DIII-D

Plasmas

10:40-11:10 Coffee Break

Session 2: TAE

Chair: W. Heidbrink

11:10-11:50 I-2: Garcia-Munoz M.

Active Control of Alfvén Eigenmodes in the ASDEX Upgrade tokamak

11:50-12:15

O-3: Dumont R.

Scenario development for the observation of alpha-driven instabilities in JET

DT plasmas

12:15-12:40

O-4: Podestà M.

Destabilization of counter-propagating Alfvénic instabilities by off-axis, co-

current neutral beam injection

12:40-14:10 Lunch Break

Session 3: Fast Ion Losses

Chair: S. Pinches

14:10-14:50 I-3: Kiptily V.G.

Recent studies of fast ions and fusion product losses on JET

14:50-15:15 O-5: Farengo R.

Alpha particle transport due to inelastic collisions

15:15-15:40 O-6: Kim J.

Fastion losses associated with the RMP applications on KSTAR

Wednesday, 6 September, 2017

Session 5: Runaways

Chair: K. Shinohara

8:30-9:10 I-5: Papp G.

Runaway electron dynamics following massive gas injection on the European

medium sized tokamaks

9:10-9:35 O-8: Hoppe M.

Modeling synchrotron radiation images of runaway electrons

9:35-10:00 O-9: Lvovskiy A.

Investigation of runaway electron dissipation in DIII-D using a gamma ray

imager


Poster Session 1


Session 6: Fast Ion Distribution

Chair: Y. Todo

14:00-14:40 I-6: Nocente M.

Observation of MeV range ions in radio frequency heating experiments with the

three ion scenarios at JET


Session 4: Mode Chirping

Chair: S. Sharapov

16:10-16:50 I-4: Wang G.

Nonlinear frequency chirping in Alfvén continuum

16:50-17:15 O-7: Duarte V.N.

Likelihood for Alfvénic instability bifurcation in experiments

17:15 Adjourn

Buses leave at 17:45

14:40-15:05 O-10: Weiland M.

Real-time simulations of the NBI fast-ion distribution function

15:05-15:30 O-11: Stagner L.

Determining the population of individual fast-ion orbits using generalized

diagnostic weight functions


Session 7: CAE and GAE

Chair: G. Vlad

16:00-16:40 I-7: Crocker N.A.

Local compressional and global Alfvén eigenmode structure on NSTX and their

effect on core energy transport

16:40-17:05 O-12: Belova E.V.

Numerical simulations of GAE stabilization in NSTX-U

17:05-17:30 O-13: Tang S.

Experimental investigation of stability, frequency and toroidal mode number of

compressional Alfvén eigenmodes in DIII-D

17:30 Adjourn


Thursday, 7 September, 2017

Session 8: Diagnostic Development

Chair: E. Fredrickson

8:30-9:10 I-8: Sharapov S.E.

MHD spectroscopy of tokamaks with pellets via Alfvén Eigenmodes

9:10-9:35 O-14: Isobe M.

Fusion neutron production with deuterium neutral beam injection and

enhancement of energetic-particle physics study in the Large Helical Device

9:35-10:00 O-15: Kiptily V.G.

Escaping alpha-particle monitor for burning plasmas


Poster Session 2


Session 9: Turbulence & Interchange Modes

Chair: W. Heidbrink

14:00-14:40 I-9: Wilkie G.J.

The stabilization of ITG turbulence induced by fast ions

14:40-15:05 O-16: Ohdachi S.

Excitation and suppression of trapped-energetic-ion driven resistive

interchange modes in LHD plasmas with intense deuterium beam injection

15:05-15:30 O-17: Testa D.

Characterization of the edge magnetic turbulence during TCV NBH discharges


Session 10: ICE & CAE

Chair: S. Pinches

16:00-16:40 I-10: Thome K.E.

Ion Cyclotron Emission on the DIII-D tokamak

16:40-17:05 O-18: Magee R.M.

Collective phenomena in the advanced, beam-driven FRC

17:05-17:30 O-19: Fredrickson E.D.

Suppression of Alfvénic modes through modifications of the fast ion distribution

17:30 Adjourn


Friday, 8 September, 2017

Session 11: GAMs and eGAMs

Chair: S. Sharapov

9:00-9:40 I-11: Zarzoso D.

Particle transport due to the nonlinear phase of energetic-particle-driven

geodesic acoustic modes in full-f gyro-kinetic simulations

9:40-10:05 O-20: Hole M.J.

Fluid models for burning plasmas: reactive EGAMs

10:05-10:30 O-21: Wang H.

Nonlinear simulations of chirping geodesic acoustic mode and the associated

half-frequency mode


Session 12: RMPs, NTMs, ELMs

Chair: K. Shinohara

11:00-11:40 I-12: Jacobsen A.S.

Transport of confined fast ions in the presence of RMP’s and MHD-induced

perturbations in ASDEX Upgrade

11:40-12:05 O-22: Heidbrink W.W.

Phase-Space Dependence of Fast-Ion Transport by Neoclassical Tearing

Modes

12:05-12:30 O-23: Galdon-Quiroga J.

Experimental evidence of beam ion acceleration during edge localized modes in

the ASDEX Upgrade tokamak


Session 13: Low Frequency Alfvén Eigenmodes

Chair: Y. Todo

14:00-14:40 I-13: Lu Z.X.

Symmetry breaking of BAE driven by energetic particles

14:40-15:05 O-24: Lin Zh.

Excitation of Low Frequency Alfven Eigenmodes in Toroidal Plasmas


Session 14: Summaries

Chair: G. Vlad

15:35-16:15 Summary of Experimental Presentations

16:15-16:55 Summary of Theory presentations

16:55-17:10 Closing remarks

17:10 End of Meeting

1

Abstracts

List of Invited:

I-1: Y. Todo, Global transport of energetic particles due to the synchronization of multiple

Alfvén eigenmodes brings about the profile resiliency (p. 9)

I-2: M. Garcia-Munoz, S. E. Sharapov, M. A. Van Zeeland, B. Bobkov, J. Ferreira, A.

Figueiredo, M. Fitzgerald, J. Galdon-Quiroga, D. Gallart, B. Geiger, J. Gonzalez-Martin, T.

Johnson, P. Lauber, M. Mantsinen, F. Nabais, V. Nikolaeva, M. Rodriguez-Ramos, L. Sanchis-

Sanchez, P. Schneider, A. Snicker, Y. Todo, P. Vallejos, B. Vanovac, the ASDEX Upgrade

Team and the EUROfusion MST1 Team, Active Control of Alfvén Eigenmodes in the ASDEX

Upgrade tokamak (p. 10)

I-3: V.G. Kiptily and JET contributors, Recent studies of fast ions and fusion product losses on

JET (p. 12)

I-4: G. Wang, H.L. Berk, B.N. Breizman, L.J. Zheng, Nonlinear frequency chirping in Alfvèn

continuum (p. 13)

I-5: G. Papp, G. Pautasso, J. Decker, D. Carnevale, J. Mlynar, P. Blanchard, D. Choi, S. Coda,

B. Duval, R. Dux, O. Embreus, B. Erdos, B. Esposito, O. Ficker, R. Fischer, C. Fuchs, C.

Galperti, L. Giannone, M. Gobbin, M. Gospodarczyk, A. Gude, M. Gruber, A. Herrmann, L.

Hesslow, M. Hoppe, F. Janky, G. Kocsis, B. Labit, K. Lackner, A. Lier, T. Lunt, E. Macusova,

M. Maraschek, L. Marelli, P. Marmillod, P.J. McCarthy, A. Mlynek, M. Nocente, E. Nardon, P.

Piovesan, V.V. Plyusnin, G.I. Pokol, P.Zs. Poloskei, S. Potzel, C. Reux, O. Sauter, B. Sieglin,

U. Sheikh, A. Shevelev, C. Sommariva, W. Suttrop, T. Szepesi, G. Tardini, M. Tardocchi, M.

Teschke, D. Testa, W. Treutterer, M. Valisa, G. Wilkie, B. Wiringer, ASDEX Upgrade Team,

TCV Team, the EUROfusion MST1 Team, Runaway electron dynamics following massive gas

injection on the European medium sized tokamaks (p. 14)

I-6: M. Nocente, Ye. O. Kazakov, V.G. Kiptily, T. Craciunescu, J. Eriksson, L. Giacomelli, G.

Gorini, C. Hellesen, E. Lerche, M. Mantsinen, J. Ongena, S. E.Sharapov, M. Tardocchi, D. Van

Eester and JET Contributors, Observation of MeV range ions in radio frequency heating

experiments with the three ion scenarios at JET (p. 16)

I-7: N. A. Crocker, E. Belova, R. B. White, E. D. Fredrickson, N. N. Gorelenkov, K. Tritz, W.

A. Peebles, S. Kubota, A. Diallo and B. P. LeBlanc, Local compressional and global Alfvén

eigenmode structure on NSTX and their effect on core energy transport (p. 18)

I-8: S.E. Sharapov, H.J.C. Oliver, B.N. Breizman, M. Fitzgerald, L. Garzotti and JET

contributors, MHD spectroscopy of tokamaks with pellets via Alfvén Eigenmodes (p. 19)

I-9: G. J. Wilkie, A. Iantchencko, I. Pusztai, E. G. Highcock, I. G. Abel, T. Fülöp, The

stabilization of ITG turbulence induced by fast ions (p. 20)

I-10: K.E. Thome, D. C. Pace, R.I. Pinsker, Y.B. Zhu, W.W. Heidbrink, Ion Cyclotron Emission

on the DIII-D Tokamak (p. 21)

2

I-11: D. Zarzoso, Particle transport due to the nonlinear phase of energetic-particle-driven

geodesic acoustic modes in full-f gyro-kinetic simulations (p. 22)

I-12: A.S. Jacobsen, B. Geiger, P. Lauber, M. Weiland, A.J. van Vuuren, A. Bock, R. Fischer,

L. Giannone, E. Poli, M. Reich, P. Schneider, M. Salewski, G. Tardini, the ASDEX Upgrade

Team and the EUROfusion MST1 Team, Transport of confined fast ions in the presence of

RMP’s and MHD-induced perturbations in ASDEX Upgrade (p. 23)

I-13: Z.X. Lu, X. Wang, Ph. Lauber, F. Zonca, Symmetry breaking of BAE driven by energetic

particles (p. 24)

3

List of Orals:

O-1: D.J. Lin, C.S. Collins, W.W. Heidbrink, J. Huang, D.C. Pace, M. Podestà, M. Van

Zeeland, and the DIII-D Team, Fast-ion profiles in discharges with Alfvén eigenmode activity

(p. 25)

O-2: M.A. Van Zeeland, W.W. Heidbrink, M. Austin, C. Collins, X.D. Du, V. Duarte, A. Hyatt,

G. Kramer, N. Gorelenkov, D. Lin, C. Luo, G. McKee, C. Muscatello, C. Petty, M. Walker and

Y.B. Zhu, Y. Zhu, Alfvén Eigenmodes and Fast Ion Transport in Negative Triangularity DIII-D

Plasmas (p. 26)

O-3: R. Dumont, J. Mailloux, V. Aslanyan, M. Baruzzo, C. D. Challis, I. Coffey, E. Delabie, J.

Eriksson, J. Ferreira, M. Fitzgerald, L. Giacomelli, C. Giroux, N. Hawkes, P. Jacquet, E. Joffrin,

T. Johnson, D. King, V. Kiptily, B. Lomanowski, E. Lerche, M. Mantsinen, S. Menmuir, K.

McClements, S. Moradi, M. Nocente, A. Patel, H. Patten, R. Scannell, S. Sharapov, E. Solano,

M. Tsalas, P. Vallejos, H. Weisen and JET contributors, Scenario development for the

observation of alpha-driven instabilities in JET DT plasmas (p. 27)

O-4: M. Podestà, E. D. Fredrickson and M. Gorelenkova, Destabilization of counter-

propagating Alfvénic instabilities by off-axis, co-current neutral beam injection (p. 28)

O-5: R. Farengo, C. Clauser, Alpha particle transport due to inelastic collisions (p. 29)

O-6: J. Kim, T. Rhee, S.I. Lee, J.-Y. Kim, Y. In, A. Loarte, K. Shinohara, M.J. Choi, and

H. Jhang, Fast-ion losses associated with the RMP applications on KSTAR (p.30)

O-7: V.N. Duarte, N.N. Gorelenkov, E.D. Fredrickson, M. Schneller, H.L. Berk, G.P. Canal,

W.W. Heidbrink, S.M. Kaye, M. Podestà, M.A. Van Zeeland and W.X. Wang, Likelihood for

Alfvénic instability bifurcation in experiments (p. 31)

O-8: M. Hoppe, O. Embréus, A. Tinguely, R. Granetz, T. Fülöp, Modeling synchrotron

radiation images of runaway electrons (p. 32)

O-9: A. Lvovskiy, C. Paz-Soldan, N.W. Eidietis, D. Pace, D. Taussig, Investigation of runaway

electron dissipation in DIII-D using a gamma ray imager (p. 33)

O-10: M. Weiland, R. Bilato, R. Dux, B. Geiger, A. Lebschy, F. Felici, R. Fischer, M. Reich,

the ASDEX Upgrade team and the Eurofusion MST1 team, Real-time simulations of the NBI

fast-ion distribution function (p. 34)

O-11: L. Stagner, W.W. Heidbrink, Determining the Population of Individual Fast-ion Orbits

Using Generalized Diagnostic Weight Functions (p. 35)

O-12: E. V. Belova, E. D. Fredrickson, N. A. Crocker, and the NSTX-U team, Numerical

simulations of GAE stabilization in NSTX-U (p. 36)

O-13: S. Tang, K.E. Thome, N. A. Crocker, D. Pace and W.W. Heidbrink, Experimental

investigation of stability, frequency and toroidal mode number of compressional Alfvén

eigenmodes in DIII-D (p. 37)

4

O-14: M. Isobe, K. Ogawa, T. Nishitani, N. Pu, H. Kawase, R. Seki, H. Nuga, E. Takada, S.

Murakami, Y. Suzuki, M. Yokoyama, M. Osakabe, and LHD Experiment Group, Fusion

neutron production with deuterium neutral beam injection and enhancement of energetic-

particle physics study in the Large Helical Device (p. 38)

O-15: V.G. Kiptily, Escaping alpha-particle monitor for burning plasmas (p. 39)

O-16: S. Ohdachi, T. Bando, M. Isobe, K. Nagaoka, Y. Suzuki, X. D. Du, K. Y. Watanabe, H.

Tsuchiya, T. Akiyama, K. Ogawa, T. Ido, A. Shimizu, Y. Narushima, M. Yoshinuma, R. Seki,

H. Takahashi, S. Sakakibara, K. Toi, M. Osakabe, T. Morisaki, and the LHD Experiment Group,

Excitation and suppression of trapped-energetic-ion driven resistive interchange modes in LHD

plasmas with intense deuterium beam injection (p. 41)

O-17: D. Testa, A. Iantchenko, L.M. Perrone, A. Tolio, B. Geiger, C. Hopf, and the TCV and

EUROfusion MST1 teams, Characterization of the edge magnetic turbulence during TCV NBH

discharges (p. 42)

O-18: R. M. Magee, A. Necas, R. Clary, M. C. Thompson, T. Roche, S. Korepanov, T. Tajima,

and the TAE Team, Collective phenomena in the advanced, beam-driven FRC (p. 43)

O-19: E. D. Fredrickson, E. V. Belova, N. N. Gorelenkov, M. Podestà and the NSTX-U team,

Suppression of Alfvénic modes through modifications of the fast ion distribution (p. 44)

O-20: M. J. Hole, M. Fitzgerald, Z. S. Qu, B. Layden, G. Bowden, R. L. Dewar, Fluid models

for burning plasmas: reactive EGAMs (p. 45)

O-21: H. Wang, Y. Todo, T. Ido, Y. Suzuki, Nonlinear simulations of chirping geodesic

acoustic mode and the associated half-frequency mode (p. 46)

O-22: W.W. Heidbrink, L. Bardoczi, C.S. Collins, G. Kramer, D. Lin, C. Muscatello, M.

Podesta, M. Van Zeeland, and Y.B. Zhu, Phase-Space Dependence of Fast-Ion Transport by

Neoclassical Tearing Modes (p. 47)

O-23: J. Galdon-Quiroga, M. Garcia-Munoz, K.G. McClements, M. Nocente, S. Freethy,

M. Hoelzl, A.S. Jacobsen, J.F. Rivero-Rodriguez, F. Orain, M. Salewski, L. Sanchis-Sanchez,

E.Viezzer, the ASDEX Upgrade and EUROfusion MST1 Teams, Experimental evidence of

beam ion acceleration during edge localized modes in the ASDEX Upgrade tokamak (p. 48)

O-24: Zh. Lin, Excitation of Low Frequency Alfven Eigenmodes in Toroidal Plasmas (p. 50)

5

List of Posters:

Poster Session I

P-1: S. Äkäslompolo, S. Bozhenkov, M. Drevlak, Y. Turkin, R. Wolf and W7-X Team, NBI

wall load simulations in the Wendelstein 7-X stellarator with ASCOT (p. 52)

P-2: L.G. Askinazi, A.A. Belokurov, D.B. Gin, V.A. Kornev, S.V. Lebedev, A.E. Shevelev,

A.S. Tukachinsky, N.A Zhubr, IC emission in NBI and ohmically heated plasmas in TUMAN-

3M tokamak (p. 53)

P-3: I Chavdarovski, M Schneller, Z Qiu and A Biancalani, Excitation of energetic particle

driven Geodesic Acoustic Modes (EGAMs) by the velocity anisotropy of ion beam with slowing

down and Maxwellian distribution (p. 54)

P-4: X.D. Du, W.W. Heidbrink, M.A. Van Zeeland and D. Su, Development of a Novel

Scintillator-Based, Imaging Neutral Particle Analyzer in DIII-D tokamak (p. 55)

P-5: G. Meng, N. N. Gorelenkov, H. L. Berk, V. N. Duarte, R. B. White, A. Bhattacharjee,

Resonance frequency broadening of wave-particle interaction in tokamaks due to collision and

microturbulence (p. 56)

P-6: N. Gorelenkov , V. N. Duarte, M. Podesta, Resonance line broadened quasilinear (RBQ)

code for fast ion Alfvénic relaxations (p. 57)

P-7: F. Camilo de Souza, A. G. Elfimov, R. M. O. Galvão, Geodesic modes driven by plasma

fluxes during auxiliary NB or ICR heating in tokamaks (p. 58)

P-8: A. K. Fontanilla, B. N. Breizman, Lifetime of Runaway Electrons at Phase-space Attractor

(p. 59)

P-9: G. Z. Hao, W. W. Heidbrink, D. Liu, L.Stagner, M. Podesta, A. Bortolon, R.Bell,

D. S. Darrow and E. D. Fredrickson, Measurement of the passive fast ion D-alpha emission on

NSTX-U (p. 60)

P-10: T. Hayward-Schneider, Ph. Lauber, Nonlinear energetic particle transport by Alfvén

eigenmodes and sensitivity study of hybrid-gyrokinetic physics models (p. 61)

P-11: M.J. Hole, B. D. Blackwell, G. Bowden, M. Cole, A. Könies, C. Michael, F. Zhao and

S. R. Haskey, Global Alfvén Eigenmodes in the H-1 heliac (p. 62)

P-12: D. Kim, M. Podestà and F. Poli, ORBIT modelling for fast particle redistribution induced

by sawtooth instability (p. 63)

P-13: G.J. Kramer, C. Holcomb, W.W. Heidbrink, C. Collins, R. Nazikian, M.A. Van Zeeland

and Y. Zhu, Suppressing Alfven eigenmodes in high-performance discharges (p.64)

P-14: T. Kurki-Suonio, J. Varje, A. Snicker and P. Vincenzi, The Effect of Ferritic Inserts on

Fast Ions in DEMO (p. 65)

6

P-15: J.B. Lestz, E.V. Belova, N.N. Gorelenkov, Energetic-particle-modified global Alfvén

eigenmodes (p.66)

P-16: D. Liu, W. W. Heidbrink, G. Z. Hao, M. Podesta, E. D. Fredrickson and D. S. Darrow,

N. A. Crocker, S. Kubota and W. W. Heidbrink, Effect of Sawtooth crashes on fast-ion

distribution in NSTX-U (p. 67)

P-17: A.V. Melnikov, E. Ascasibar, A. Cappa, F. Castejon, L.G. Eliseev, C. Hidalgo,

P.O. Khabanov, N.K. Kharchev, A.S. Kozachek, L.I. Krupnik, M. Linier, S.E.Lysenko,

J.L. dePablos, V.N. Zenin, A.I. Zhezhera, and TJ-II team, Detection and investigation of Alfven

Eigenmodes with Heavy Ion Beam Probe in the TJ-II stellarator (p. 68)

P-18: J. Morimoto, R. Seki, Y. Suzuki, Quantitative evaluation of the wall heat load by lost fast

ions in the Large Helical Device (p. 69)

P-19: F. Nabais, V. Aslanyan, D. Borba, R. Coelho, R. Dumont, J. Ferreira, A. Figueiredo,

M. Fitzgerald, J. Mailloux, P. Rodrigues, P. Puglia, S. E. Sharapov and JET Contributors, TAE

stability calculations compared to TAE antenna results in JET (p. 70)

P-20: K. Nagaoka, A. Azegami, M. Osakabe, M. Isobe, K. Ogawa, Y. Suzuki, R. Seki,

S. Kamio, M. Shibuya, H. Yamaguchi, S. Kobayashi, S. Yamamoto, K. Nagasaki, A. Cappa,

J.M. Fontdecaba, and E. Ascasibar, Nonlinear interaction of fast ions with Alfvén eigenmodes -

Control and measurement of distribution function of fast ions (p. 71)

Poster Session II

P-21: H. Nuga, R. Seki, S. Kamio, M. Osakabe, M. Yokoyama, M. Isobe, K. Ogawa, and LHD

experiment group, Experimental evaluation of nonlinear collision effect on the beam slowing-

down process (p. 72)

P-22: S.D. Pinches, R.J. Akers, G.T.A Huijsmans, T. Jonsson, Ph. Lauber, M. Salewski,

M. Schneider, S.E. Sharapov, S. Ward, ITPA Energetic Particle Physics Topical Group and

IMAS Contributors, Energetic Particles within ITER’s Integrated Modelling & Analysis Suite

(p. 73)

P-23: V.V. Plyusnin, V.G. Kiptily, A.E. Shevelev, E.M. Khilkevitch and JET contributors, Hard

X-ray Bremsstrahlung of Relativistic Runaway Electrons in JET (p. 74)

P-24: P. Zs. Poloskei, G. Papp, G. I. Pokol, Ph. W. Lauber, X. Wang, L. Horvath and the

ASDEX Upgrade team, Analysis of the nonlinear interaction of fast ion driven plasma waves

(p. 76)

P-25: L. Sanchis, M. Garcia-Munoz, A. Snicker, J. Galdon-Quiroga, D. A. Ryan, M. Nocente,

J. F. Rivero-Rodriguez, L. Chen, W. Suttrop, E. Viezzer, M. A. Van Zeeland, ASDEX Upgrade

and EUROfusion MST1 Teams, Fast-Ion Edge Resonant Transport Layer Induced by

Externally Applied 3D Fields in the ASDEX Upgrade Tokamak (p. 77)

7

P-26: A. K. Sanyasi, L. M. Awasthi, P. K. Srivastava, S. K. Mattoo, D. Sharma, P. Srivastav,

R. Sugandhi, R. Singh, R. Paikaray and P. K. Kaw, Demonstration of Loss Cone Induced Quasi-

Longitudinal (QL) Whistlers in Large Laboratory Plasma of LVPD (p. 79)

P-27: D. Sanz-Orozco, H. L. Berk, The breakdown of the weakly-nonlinear regime for kinetic

instabilities (p. 80)

P-28: M. Schneller, G.Y. Fu, I. Chavdarovski, W.X. Wang, Ph. Lauber, Z.X. Lu, What shapes

the radial structure of energetic particle induced geodesic acoustic modes?(p. 81)

P-29: R. Seki, Y. Todo, Y. Suzuki, K. Ogawa, M. Isobe, and M. Osakabe, Comprehensive

magnetohydrodynamic hybrid simulations of fast ion driven Alfvén eigenmodes and fast ion

losses in the Large Helical Device (p. 82)

P-30: K. Shinohara, A. Bierwage, Y. Suzuki, J. Kim, G. Matsunaga, M. Honda, T. Rhee,

Estimation of orbit island width from static magnetic island width, using safety factor and orbit

pitch (p. 83)

P-31: C. Slaby, A. Könies, and R. Kleiber, Effects of collisions on the saturation dynamics of

TAEs in tokamaks and stellarators (p. 84)

P-32: D. A. Spong, L. Carbajal Gomez, D. del Castillo Negrete, L. Baylor, Simulation of

runaway electrons in tokamaks with pellet suppression and instability effects (p. 85)

P-33: L.Stipani, D.Testa, A.Fasoli, M.Fontana, A.Karpushov, C.Marini, L.Porte, and TCV

contributors, Fishbones and de-trapping of fast ions during NBH discharges on TCV (p. 86)

P-34: T. Bando, S. Ohdachi, M. Isobe, K. Nagaoka, Y. Suzuki, X. D. Du, K. Y. Watanabe,

Y. Narushima, K. Ogawa, H. Tsuchiya, T. Akiyama, T. Ido, A. Shimizu, M. Yoshinuma,

S. Masuzaki, T. Ozaki, R. Seki, H. Takahashi, K. Toi, M. Osakabe, T. Morisaki and the LHD

Experiment Group, Effects of Trapped Energetic-Ion-Driven Resistive Interchange Modes on

Deuterium Beam Ions and Background Plasmas of LHD (p. 87)

P-35: A. V. Tykhyy, Stochastic diffusion of energetic ions in Wendelstein-type stellarators

(p. 88)

P-36: J. Varela, D. Spong and L. Garcia, Alfven Eigenmodes stability in 3D configurations

using a Landau-closure model (p. 89)

P-37: G. Vlad, S. Briguglio, G. Fogaccia, V. Fusco, C. Di Troia, E. Giovannozzi, X. Wang,

Single-n versus multiple-n simulations of Alfvénic global modes (p. 90)

P-38: B. J. Q. Woods, B. N. Breizman, and R. G. L. Vann, Two-mode dynamics of phase-space

holes and clumps in systems near marginal stability (p. 91)

P-39: L. Xu, L. Hu, Y. Yuan, Y. Li, G. Zhong, H. Liu, K. Chen, T. Shi and Y. Duan, Fishbone

oscillations in EAST (p. 92)

P-40: M. Xu, J. Zhang, Y. Duan, T. Shi, S. Mao, Sh. Lin, L. Hu, and the EAST Team,

Experimental Observation of Energetic Particle Induced Geodesic Acoustic Mode in EAST

Tokamak (p. 93)

8

P-41: F.S. Zaitsev , N.N. Gorelenkov, M.P. Petrov, V.I. Afanasyev, M.I. Mironov, Sawtooth

mixing of alphas, knock-on D, T ions and its influence on NPA spectra in ITER plasma (p. 94)

P-42: L.E. Zakharov, N.N. Gorelenkov, Plasma equilibrium with fast ion orbit width, velocity

anisotropy and toroidal flow effects (p. 95)

P-43: Ch. Liu, E. Hirvijoki, D. P. Brennan, A. Bhattacharjee, Excitation of whistler waves and

magnetized plasma waves by runaway electrons in tokamaks (p. 96)

P-44: D.C. Pace, Manipulating Energetic Ion Velocity Space to Control Instabilities and

Improve Tokamak Performance (p. 97)

P-45: G. Y. Fu, L. M. Yu, F. Wang, Low-Frequency Fishbone Driven by Passing Fast Ions in

Tokamak Plasmas (p. 98)

9

I-1: Global transport of energetic particles due to the synchronization of multiple Alfvén

eigenmodes brings about the profile resiliency

Y. Todo1,2

1

National Institute for Fusion Science, Toki, Gifu 509-5292, Japan 2

SOKENDAI (The Graduate University for Advanced Studies), Toki, Gifu 509-5292, Japan

Alfvén eigenmodes (AEs) driven by energetic particles in tokamak plasmas and the energetic

particle distribution formed with the AEs, neutral beam injection, and collisions are investigated

with hybrid simulations for energetic particles and a magnetohydrodynamic fluid [1]. The multi-

phase simulation [2], which is a combination of classical simulation and hybrid simulation, is

applied for various beam deposition power PNBI and slowing-down time (s). The physical

parameters other than PNBI and s are similar to those of a TFTR experiment [3]. It was found

that the intermittency of AEs rises with increasing PNBI and increasing s. With increasing

volume-averaged classical energetic ion pressure, which is well proportional to PNBIs, the

energetic ion confinement degrades monotonically due to the transport by the AEs. The

energetic ion pressure profile resiliency, where the increase in energetic ion pressure profile is

saturated, is found for the cases with the highest PNBIs where the AE bursts take place. Figure 1

compares the radial profile evolutions of energetic ion trasport flux between case I (PNBI=5MW

and s=20ms) where the amplitude of the dominant AE is kept at a constant and low level, and

case II (PNBI=10MW and s=100ms, which are similar to the TFTR experiment) where the AE

bursts take place. We see that the synchronization of multiple AEs generates the global and huge

transport flux leading to the profile resiliency.

Figure 1. Radial profile evolutions of energetic ion transport flux for cases I and II.

References:

[1] Y. Todo, New J. Phys. 18 (2016) 115005.

[2] Y. Todo et al., Nucl. Fusion 54 (2014) 104012.

[3] K. L. Wong et al.,Phys. Rev. Lett. 66 (1991) 1874.

10

I-2: Active Control of Alfvén Eigenmodes in the ASDEX Upgrade tokamak

M. Garcia-Munoz1, S. E. Sharapov

2, M. A. Van Zeeland

3, B.Bobkov

4, J.Ferreira

5,

A.Figueiredo5, M.Fitzgerald

1, J.Galdon-Quiroga

2, D.Gallart

6, B.Geiger

4, J. Gonzalez-Martin

2,

T.Johnson7, P.Lauber

4, M.Mantsinen

6, F.Nabais

5, V.Nikolaeva

4, M.Rodriguez-Ramos

2,

L.Sanchis-Sanchez2, P.Schneider

4, A. Snicker

8, Y. Todo

9, P.Vallejos

7, B. Vanovac

10 , the

ASDEX Upgrade Team and the EUROfusion MST1 Team*

1FAMN Department, Faculty of Physics, University of Seville, Seville, Spain

2CCFE, Culham Centre for Fusion Energy, Abingdon, Oxfordsh14 3DB, UK

3General Atomics, PO Box 85608, San Diego, USA

4Max Planck Institute fur Plasmaphysik, Garching, Germany

5Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Portugal

6Barcelona Supercomputing Center (BSC), Barcelona, Spain

7VR / Royal Institute of Technology KTH, Sweden

8Aalto University, Aalto, Finland

9National Institute for Fusion Science, Toki, Gifu 509-5292, Japan

10

FOM-Institute DIFFER, Dutch Institute for Fundamental Energy Research

E-mail of Corresponding Author: [email protected]

External actuators are commonly used to control /

suppress magnetohydrodynamic (MHD)

fluctuations in magnetically confined fusion

devices. During the past years, localized Electron

Cyclotron Resonant Heating (ECRH), Electron

Cyclotron Current Drive (ECCD) and externally

applied 3D fields have been applied in the

ASDEX Upgrade (AUG) tokamak to control fast-

ion driven Alfvén Eigenmodes (AEs). Reversed

Shear Alfven Eigenmodes (RSAEs) destabilized

by Neutral Beam Injection (NBI) are completely

suppressed by ECRH localized near qmin. LIGKA

simulations indicate that the beta suppression

mechanism [1] plays a key role due to a pressure

driven upshift of the Geodesic Acoustic Mode

(GAM) continuum. Toroidally Induced Alfvén

Eigenmodes (TAEs) driven unstable by Ion

Cyclotron Resonant Heating (ICRH), in contrast, are facilitated by localized off-axis ECRH as

shown in the figure. Detailed TAE stability calculations have been carried out with the

CASTOR-K, HAGIS, and LIGKA codes using fast-ion distributions computed with the PION

and SELFO codes. A significant peaking in Te profile caused by ECRH is found to increase the

fast-ion slowing down time and fast-ion pressure significantly, while increase in the density

caused a sweeping of the TAE frequency, thereby affecting the resonance condition. Externally

applied 3D fields have also been observed to have a strong impact on the fast-ion population and

associated AEs. This depends, however, on q95, the spectra of the applied perturbation and the

fast-ion distribution. Non-linear hybrid MEGA simulations indicate that the externally applied

3D fields, depending on their spectra, can significantly modify the AE growth rate, mode

* See H. Meyer et al., Nucl. Fusion FEC 2016 Special issue (2017)

TAEs

Time (sec)

Fig.1. AUG shot #33145. Magnetic

spectrogram showing the AE activity during

an ICRF heated discharge. The timing of the

ICRH, ECRH and density evolution is

overplotted in green and white.


11

saturation amplitude and radial structure. Overall, the results presented here suggest that a

variety, and promising, set of external actuators may be used to alter the fast-ion distribution and

associated AE stability. Their applicability to ITER will be discussed.

References:

[1] E. D. Fredrickson et al., Phys. Plasmas 14, 102510 (2007)

12

I-3: Recent studies of fast ions and fusion product losses on JET

V.G. Kiptily and JET contributors*

CCFE, UK Atomic Energy Authority, Culham Science Centre, Abingdon OX14 3DB, UK


This paper presents recent results on fast ion studies on JET. The JET machine with ITER-like

wall (a beryllium wall and tungsten divertor) is equipped with upgraded auxiliary heating

systems, therefore possible future deuterium-tritium experiments on JET are expected to

produce a significant population of -particles at plasma parameters approaching as closely as

possible to the ITER values giving a great opportunity to study fusion alphas. A set of

diagnostics for both confined and lost fast ions was employed for investigating the response of

fast ions to MHD modes. The development of high performance discharge scenarios, both

“baseline” H-mode and “hybrid” with q0 above 1, as well as developing a dedicated scenario to

establish a stationary high fusion yield DT plasma at high qmin for -driven AE modes studies in

the forthcoming full-scale DT experiments was a main priority of recent campaigns at JET.

In high performance hybrid scenario experiments an increased level of fast ion losses in the

MeV energy range was observed during the instability of high-frequency n=1 fishbones. The

fishbones are excited during deuterium neutral beam injection combined with ion cyclotron

heating. The frequency range of the fishbones, 10 – 25 kHz, indicates that they are driven by a

resonant interaction with the NBI-produced D beam ions in the energy range ≤120 keV. The fast

particle losses in a much higher energy range are measured with a fast ion loss detector, and the

data show an expulsion of deuterium plasma fusion products, 1 MeV tritons and 3 MeV protons,

during the fishbone bursts. An MHD mode analysis with the MISHKA code combined with the

nonlinear wave-particle interaction code HAGIS shows that the loss of toroidal symmetry

caused by the n=1 fishbones affects strongly the confinement of non-resonant high energy

fusion-born tritons and protons by perturbing their orbits and expelling them. This modelling is

in a good agreement with the experimental data.

In the baseline scenario, significant changes in the fusion product losses were found to be

associated with L–H confinement transitions in the plasma. After the L–H transition, a decrease

of the prompt fusion product loss fraction was observed. In experiments devoted to development

of scenarios for the -particle wave-interaction studies an effect of TAEs on the fusion product

confinement has been found. Fusion product loss measurements make it possible to select an

optimized scenario regarding TAE excitation and minimizing the fast ion loss fraction.

This work has been carried out within the framework of the EUROfusion Consortium and has

received funding from the Euratom research and training programme 2014-2018 under grant

agreement No 633053 and from the RCUK Energy Programme [grant No EP/P012450/1]. To

obtain further information on the data and models underlying this paper please contact

[email protected] . The views and opinions expressed herein do not necessarily

reflect those of the European Commission.

* See the author list of “Litaudon et al, Overview of the JET results in support to ITER, accepted for publication in

Nuclear Fusion”



13

I-4: Nonlinear frequency chirping in Alfvèn continuum

G. Wang, H.L. Berk, B.N. Breizman, L.J. Zheng

Institute for Fusion Studies, University of Texas at Austin

Fast frequency sweeping leading to ‘TAE avalanche’ events have been observed in NSTX*,

where the frequency emerges around the TAE gap and rapidly decreases to low frequency. Here

we attempt to replicate the initiation of this fast frequency chirping using the code, CHIRP,

based on a mapping technique for the change of the equilibrium orbits due to the particle wave

interaction. We solve for both the self-consistent nonlinear wave-energetic particle resonant

interaction and its self-consistent mode structure that depends upon the resonant energetic

particle pressure. In order to use a larger time step based on the wave-particle trapping

frequency, rather than the much larger wave frequency, CHIRP has been automatically adapted

to calculate the appropriate time step. The calculation demonstrates that when the EP stored

energy density, 𝛽𝐸𝑃(𝑡), increases, TAE mode is first excited with a limited range of chirping,

until the energetic particle mode (EPM)† threshold is reached. Then strong chirping emerges in

the lower continuum close to the TAE gap, which chirps rapidly to lower frequencies as shown

in Fig.1 (a). An adiabatic theory is formulated that accurately describes the late time evolution.

This strong correlation between adiabatic theory and simulation thereby implies that the EPM-

trapped particles evolve with their action conserved. These trapped particles then produce large

resonant currents, that allows a large amplitude mode to occur far from the linearly predicted

frequencies. Fig.1 (b) compares the theoretical separatrix with the apparent separatrix implied

by the entrained iso-color contours of constant distribution function within the particle trapping

region. In addition, we expanded our study to account for the ideal MHD nonlinear corrections

to the linear response of the plasma. We included the zonal flow component (n=0, m=0) and its

nonlinear feedback to the fundamental frequency and found that the MHD nonlinearity doesn't

significantly alter the frequency chirping response that is predicted by the calculation that

neglects the MHD nonlinearity.

(a) (b)

Fig. 1: (a) Evolution of TAE and EPM mode spectrum with increasing EP's normalized beta (𝛽𝐸𝑃(𝑡)). The frequency region, −1 < 𝜔 < 1, is the location of the TAE gap. (b) The separatrix of a clump in

phase space is close to the inserted theoretical curve (in white), where the resonance angle 𝜒 ≡ 𝑛𝜑 −

𝑝𝜃 − ∫ 𝜔(𝜏)𝑑𝜏𝑡

0 is the coordinate and the normalized canonical momentum is 𝛺 ≡

𝑣∥

𝑅(𝑛 −

𝑝

𝑞(��)) − 𝜔(𝑡)

on the vertical axis for the particle resonance (n, p). For this case p=m+1.

* M. Podesta, et. al. Nuclear Fusion 52, 094001, (2012)

† L. Chen, Phys. Plasmas 1, 1519, (1994)

14

I-5: Runaway electron dynamics following massive gas injection on the European medium

sized tokamaks

G. Papp1, G. Pautasso

1, J. Decker

2, D. Carnevale

3, J. Mlynar

4, P. Blanchard

2, D. Choi

2,

S. Coda2, B. Duval

2, R. Dux

1, O. Embreus

5, B. Erdos

6, B. Esposito

7, O. Ficker

4, R. Fischer

1,

C. Fuchs1, C. Galperti

2, L. Giannone

1, M. Gobbin

8, M. Gospodarczyk

3, A. Gude

1, M. Gruber

1,

A. Herrmann1, L. Hesslow

5, M. Hoppe

5, F. Janky

1, G. Kocsis

9, B. Labit

2, K. Lackner

1, A. Lier

1,

T. Lunt1, E. Macusova

4, M. Maraschek

1, L. Marelli

8, P. Marmillod

2, P.J.McCarthy

10,

A. Mlynek1, M. Nocente

11, E. Nardon

12, P. Piovesan

8, V.V. Plyusnin

13, G.I. Pokol

6,

P.Zs. Poloskei6, S. Potze

l1, C. Reux

12, O. Sauter

2, B. Sieglin

1, U. Sheikh

2, A. Shevelev

14,

C. Sommariva12

, W. Suttrop1, T. Szepesi

9, G. Tardini

1, M. Tardocchi

11, M. Teschke

1, D. Testa

2,

W. Treutterer1, M. Valisa

8, G. Wilkie

5, B. Wiringer

1, ASDEX Upgrade Team

1, TCV Team

2,

the EUROfusion MST1 Team*

1Max-Planck-Institute for Plasma Physics, Garching, Germany

2Swiss Plasma Centre, EPFL, Lausanne, Switzerland

3Universita di Roma "Tor Vergata", Italy

4Institute of Plasma Physics AS CR, Prague, Czech Republic

5Chalmers University of Technology, Göteborg, Sweden

6Institute of Nuclear Techniques, BME, Budapest, Hungary

7ENEA sulla Fusione, C.R. Frascati, Italy

8Consorzio RFX, Padova, Italy

9Wigner Research Centre for Physics (HAS), Budapest, Hungary;

10Department of Physics, University College Cork, Cork, Ireland

11

Universita di Milano-Bicocca, Milano, Italy

12

CEA, IRFM, F-13108 Saint Paul Lez Durance, France

13

Instituto de Plasmas e Fusao Nuclear, IST, Universidade de Lisboa, Portugal 14

Ioffe Physical-Technical Institute (RAS), St. Petersburg, Russia;


The uncontrolled loss of a disruption-generated relativistic runaway electron (RE) beam is

intolerable in large tokamaks, and therefore the issue of how to avoid or mitigate the RE beam

is of prime importance for ITER. The tokamaks participating in the EUROfusion Medium

Sized Tokamak (MST1) campaign are executing a coordinated experimental program to better

understand RE generation, control and mitigation.

On ASDEX Upgrade (AUG) runaway electrons are routinely generated in a well reproducible

manner using in-vessel argon massive gas injection (MGI) into low-density, high temperature,

circular discharges [1, 2]. The scaling of the initial runaway current has a nonlinear dependence

on predisruption plasma-and MGI parameters, and is analyzed using 1D disruption-runaway

simulations [3]. The dissipation of the RE current however scales very well with the amount

and atomic number of the gas injected either to trigger the disruption, or afterwards to suppress

the beam. The effect of argon and neon MGI on RE current dissipation shows good agreement

with state-of-the-art kinetic models [4].

The main goal of RE experiments carried out on TCV [2, 5] – of which both quiescent and

post-disruptive are possible – is to utilize TCV’s flexible plasma shape and position control to

* See H. Meyer et al., Nuclear Fusion FEC 2016 Special Issue (2017)


15

determine the direct and indirect effects of geometry on RE generation and dissipation. While

MGI on TCV cannot deliver material into the beam as efficiently as on AUG, we found that the

plasma position with respect to the MGI valve plays a major role in gas penetration and

subsequent RE dissipation. Further studies on these issues are planned for this summer

campaign and results of these scans – along with theoretical comparisons – are planned to be

presented in this contribution.

References:

[1] G. Pautasso et al. Plasma Physics and Controlled Fusion, 59 (1):014046 (2017).

[2] G. Papp et al. IAEA-FEC, IAEA-CN-234-0502:EX/9 (2016).

[3] G. Papp et al. Nuclear Fusion, 53 (12):123017 (2013).

[4] L. Hesslow et al. Phys. Rev. Lett., 118:255001 (2017).

[5] S. Coda et al. Nuclear Fusion, 57 (10):102011 (2017).

http://stacks.iop.org/0741-3335/59/i=1/a=014046

https://nucleus.iaea.org/sites/fusionportal/Shared%20Documents/FEC%202016/fec2016-preprints/preprint0502.pdf


https://link.aps.org/doi/10.1103/PhysRevLett.118.255001


16

I-6: Observation of MeV range ions in radio frequency heating experiments with the three

ion scenarios at JET

M. Nocente1, Ye. O. Kazakov

2, V.G. Kiptily

3, T. Craciunescu

4, J. Eriksson

5, L. Giacomelli

1,

G. Gorini1, C. Hellesen

5, E. Lerche

2, M. Mantsinen

6, J. Ongena

2, S. E.Sharapov

3,

M. Tardocchi1, D. Van Eester

2 and JET Contributors

*

1Dipartimento di Fisica and Istituto di Fisica del Plasma, Milano, Italy

2Laboratory for Plasma Physics, LPP-ERM/KMS, TEC Partner, Brussels, Belgium

3Culham Centre for Fusion Energy, Culham Science Centre, Abingdon, UK

4National Institute for Laser, Plasma and Radiation Physics, Bucharest, Romania

5Department of Physics, Uppsala University, Uppsala, Sweden

6Barcelona Super Computing Centre and ICREA, Barcelona, Spain


The use of radio frequency (RF) waves is a standard tool to generate MeV-energy ions for fast-

ion physics studies in non-activated plasmas. In previous experiments, an ion cyclotron

resonance heating (ICRH) scenario has been developed to mimic D-T fusion-born alpha

particles with third harmonic acceleration of 4He ions injected by neutral beams [1]. Recent JET

experiments [2] demonstrated that energetic ions can be also effectively generated with ICRH in

three-ion plasmas by placing the cyclotron resonance position of a third ion in vicinity of the

mode conversion layer determined by the two majority species .

In this work, we present and discuss the

experimental evidence of fast-ion generation

with the three-ion heating scenario at JET. We

present data from two different experiments in

H-D plasma mixtures aimed at accelerating 3He

and D-NBI ions to MeV-range energies. A broad

set of advanced nuclear diagnostics, which

include high resolution neutron and gamma-ray

spectrometers, a gamma-ray camera and a fast

ion loss detector was used to study the energy

and space distribution of the energetic ions. In

the 3He experiment, the observation of a rich

spectrum of gamma-ray lines from the de-

excitation of 11

B and 11

C nuclei born from

reactions between fast 3He ions and

9Be

impurities testifies the most energetic 3He

population ever achieved in JET plasmas with

an ITER like wall. When a +π/2 phasing of the

ICRH antenna is used and the RF wave is

launched toroidally in the co-current direction, tomographic images of the gamma-ray

emissivity reveal a radial pinch effect on the fast ion density, which is correlated with the onset

of Alfvén Eigenmodes in the magnetic spectrogram. The latter redistribute ions and induce

crashes of previously stabilized sawteeth.

* See X. Litaudon et al, “Overview of the JET results in support to ITER”, accepted for publication in Nuclear

Fusion

Fig. 1. Gamma-ray emission spectrum measured

in JET plasmas with 3He heating in H-

D ≈ 70%:30% plasma (red) and 3He minority

heating in H plasma (blue). The different peaks

come from nuclear reactions between energetic 3He ions and

9Be impurities and unambiguously

show the significantly larger fast ion population

generated in the three-ion (3He)H-D scenario.


17

In the deuterium heating scenario, neutral beam ions are accelerated to the MeV range as they

absorb the wave power in the vicinity of the mode conversion layer through their Doppler-

shifted cyclotron resonance. Neutron measurements reveal a highly non thermal spectrum and

the rate shows a tenfold increase, which is accompanied by gamma-ray emission from d+9Be

reactions. As in the 3He case, sawteeth are stabilized and Alfvén activity is manifested in the

magnetic spectrogram.

The relevance of these results for fast 4He ion studies in non-activated plasmas in preparation of

deuterium-tritium experiments at JET and ITER is discussed.

References:

[1] M.J. Mantsinen et al., Phys. Rev. Lett. 88, 105002 (2002)

[2] Ye.O. Kazakov et al., Nature Physics, published online http://dx.doi.org/10.1038/nphys4167

18

I-7: Local compressional and global Alfvén eigenmode structure on NSTX and their effect

on core energy transport

N. A. Crocker,1 E. Belova,

2 R. B. White,

2 E. D. Fredrickson,

2 N. N. Gorelenkov,

2 K. Tritz,

3

W. A. Peebles,1 S. Kubota,

1 A. Diallo

2 and B. P. LeBlanc

2

1University of California, Los Angeles

2Princeton Plasma Physics Laboratory

3The Johns Hopkins University

4Nova Photonics, Princeton, NJ


A novel method for localized, absolute reflectometer measurements of density fluctuations

𝛿𝑛using a synthetic reflectometer diagnostic has provided new insight into compressional

(CAE) and global (GAE) Alfvén eigenmode amplitude, structure, and associated energy

transport in NSTX spherical torus. The new technique is significantly more accurate than

previous analysis producing substantially different amplitudes. CAE and GAE activity has been

shown to correlate with core anomalous electron thermal transport in high-power beam heated

NSTX plasmas [Stutman PRL09] making these measurements of significant interest. High

frequency modes (17–33% 𝑓𝑐𝑖 ) are identified as GAEs and CAEs in a 6 MW beam heated

plasma. The synthetic diagnostic allows direct testing of HYM, a leading code for CAE and

GAE stability computations that predicts substantial energy transport via CAE-KAW coupling

in these plasmas. Measured GAE structures peak near the edge, decreasing towards the core,

where they have broad, flat structures with 𝛿𝑛/n~10-4

–10-5

. In contrast, CAEs have large broad

peaks in the core 𝛿𝑛/n~10-4

–10-3

and smaller edge 𝛿𝑛. The measurements of the GAE are used

in conjunction with theory for mode induced stochastization of electron drift orbits [Gorelenkov

NF 2010] to predict the core electron thermal diffusivity (𝜒𝑒 ). GAEs are found to have

amplitudes significantly smaller than needed to explain the anomalously high 𝜒𝑒. This theory

has recently been modified to include the effects of CAEs on thermal transport and preliminary

results predict negligible increase in 𝜒𝑒. Linear simulations with HYM predict GAEs with mode

structures similar to those described above. The measurements, novel synthetic diagnostic and

simulation testing are providing invaluable insight into GAE/CAE physics and are necessary

steps towards our goal of a predictive capability.

This work was supported by U.S. DOE Contracts DE-SC0011810, DE-FG02-99ER54527 and

DE-AC02-09CH11466.


19

I-8: MHD spectroscopy of tokamaks with pellets via Alfvén Eigenmodes

S.E.Sharapov1, H.J.C.Oliver

2,1, B.N.Breizman

2, M.Fitzgerald

1, L.Garzotti

1

and JET contributors*

1CCFE, Culham Science Centre, Abingdon, OX14 3DB, UK

2Institute for Fusion Studies, University of Texas at Austin, Austin, Texas, USA

Alfvén Eigenmodes (AEs) are routinely seen in present-day magnetic fusion machines with RF

and/or NBI heating. Measurements of AEs represent an attractive form of MHD spectroscopy as

AEs are seen as numerous discrete modes, they are easily detectable even at low amplitudes, and

they do not usually cause significant deterioration in plasma confinement [1]. We assess

possible use of AEs for diagnosing tokamak plasmas with pellet injection. Injection of high-

velocity pellets into plasma is one of the main techniques for fuelling the plasma core and for

controlling ELMs [2]. Diagnostics of temporal evolution of the ablated pellet, as well as physics

effects determining transport of the pellet-produced plasma are of high importance for validating

pellet ablation models and extrapolating them towards ITER. Temporal evolution of a pellet

with its ablation time of ~1-2 ms and the diffusion/relaxation of the post pellet profile with

characteristic time of ~ 50 ms does require diagnostics with high time resolution, and AEs with

its high sensitivity to plasma density could be an attractive option. A series of JET discharges

with pellets and ICRH-driven AEs is investigated. Figures 1,2 show an example of TAEs

observed during pellet injection causing an increase in plasma density on a time scale << 50 ms.

Several effects on TAE are observed: 1) frequency of the TAEs throughout the pellet injection

sweeps down by ~30%, 2) TAE amplitudes increase, and 3) spectrum of toroidal mode numbers

of TAEs broadens after the pellet injection. The effects observed are interpreted in terms of a

significant rise in plasma density, an enhancement of mode amplitude resulting from the

resonance sweeping [3], and changes in TAE spectrum due to 3D density perturbations during

the pellet injection.

Fig.1 Magnetic spectrogram showing increase in TAE

amplitudes and sweep in TAE frequencies following

pellet injection at ~ 57.9 s in JET discharge #49044.

Fig.2 Magnetic phase spectrogram showing increase

in the spectrum of toroidal mode numbers during

pellet injection in discharge #49044.

References:

[1] S.E. Sharapov et al., Phys. Lett. A289 127 (2001);[2] L.Garzotti et al., Nucl. Fusion 46 (2006) 73; [3]

H.L.Berk, B.N.Breizman, Enhancement of particle-wave energy exchange by resonance sweeping,

Preprint IFSR #722 (1996).



agreement No 633053. The views and opinions expressed herein do not necessarily reflect those

of the European Commission.

* See the author list of “Overview of the JET results in support to ITER” by X. Litaudon et al. to be published in

Nuclear Fusion Special issue on the 26th FEC (Kyoto, Japan, 17-22 Oct 2016)

20

I-9: The stabilization of ITG turbulence induced by fast ions

G. J. Wilkie, A. Iantchencko, I. Pusztai, E. G. Highcock, I. G. Abel, T. Fülöp

Chalmers University of Technology, Gothenburg, Sweden


In recent years, it has been observed that both electromagnetic effects, due to increasing plasma

β, and the presence of certain fast particle populations suppress transport from ITG turbulence.

This effect was discovered via detailed numerical simulations of JET discharges [1]. Further

work has investigated these effects in the context of experimental scenarios [2,3], but the

underlying physics remains unresolved. However, in pursuit of increased performance,

experiments will continue to push to ever-higher β , potentially increasing the importance of this

effect. Similarly, burning plasmas will always have self-generated fast ion populations, whose

properties may differ significantly from the energetic particle populations in current

experiments. Thus, understanding the physics behind this suppression is critical to extrapolating

its importance for future devices, including ITER.

Our analysis of the physical mechanisms comprises two parts: a study of the linear physics, and

targeted nonlinear simulations. Firstly, an in-depth study of the linear physics is performed to

disentangle the competing effects upon the ITG mode. These effects include dilution of the main

ions by fast ions, changes to the pressure gradients in the plasma, and the active kinetic response

of the fast ions. To clarify these results we derive a simplified dispersion relation for

electromagnetic ITG including a fast ion population, and use it to develop a reduced model for

predicting the fast-ion-induced stabilization.

Guided by our linear results, we use nonlinear simulations to examine the structure of the

turbulence when it is stabilized by fast ions. Through this study, we show which effects lead to a

reduction of stiffness, and why. We also explore which effects lead to changes in the nonlinear

upshift of the critical temperature gradient. We diagnose which of these physical mechanisms

contribute to the experimentally-observed reduction in turbulence. Given this physical

understanding, we identify which class of fast ions contribute most beneficially to this reduction

and the conditions under which the electromagnetic stabilization is most effective. We conclude

by extrapolating these results towards ITER and DEMO.

References:

[1] J. Citrin et al. Nonlinear Stabilization of Tokamak Microturbulence by Fast Ions. Phys. Rev. Lett.,

111:155001, 2013.

[2] J Garcia et al. Key impact of finite-beta and fast ions in core and edge tokamak regions for the

transition to advanced scenarios. Nucl. Fusion, 55:053007, 2015.

[3] H Doerk et al. Gyrokinetic study of turbulence suppression in a JET-ILW power scan. Plasma Phys.

Control. Fusion, 58:115005, 2016.


21

I-10: Ion Cyclotron Emission on the DIII-D Tokam

K.E. Thome1, D. C. Pace

2, R.I. Pinsker

2, Y.B. Zhu

3, W.W. Heidbrink

3

1Oak Ridge Associated Universities, Oak Ridge, TN

2General Atomics, P.O. Box 85608, San Diego, CA 92186-5608

3University of California – Irvine, Irvine, CA

E-mails of Corresponding Authors: [email protected]

Ion Cyclotron Emission (ICE) is readily excited in DIII-D plasmas by the injection of neutral

beam ions across a wide variety of DIII-D operational space. ICE is known to be excited by

suprathermal fusion products, beam ions, or ICRF ions and has previously been observed in

many tokamaks from JET to TFTR to ASDEX-Upgrade. Understanding the relationship

between ICE and the energetic particle distribution is important in modern-day tokamaks, since

passive measurements of ICE in a reactor environment, such as ITER, could provide a way to

identify the location of alpha particles and possibly fast-ion losses [KG McClements, NF 2015].

A large collection of ICE measurements on the DIII-D tokamak have been collected over the

past two years with both fast wave antenna straps and dedicated magnetic probes digitized at

200 MHz.

This database of DIII-D ICE measurements is currently under investigation to understand the

emission’s relationship with the energetic particle distribution and provide information for an

ongoing ITPA experiment. The fundamental ICE frequency observed in DIII-D plasmas is in the

5-20 MHz range with typical toroidal magnetic fields of 1–2 T. These frequencies correspond to

both core and edge locations; however, ICE is more often observed in the edge. Harmonics of

the ICE fundamental are observed up to 100 MHz and ICE has been observed in both deuterium

and helium plasmas. As of yet, ICE in DIII-D has only been correlated with neutral-beam drive.

The frequency dependence of ICE on beam geometry, injection voltage, and power will be

presented. The unique neutral beam system (tangential and perpendicular injection, co and

counter-Ip injection) on DIII-D allows ICE to be correlated with these different beam

geometries. Strong ICE dependencies on plasma characteristics are also observed, particularly

the relationship between ICE intensity and plasma density. Relationships between ICE

observations and plasma species, toroidal field, neutron rate, etc., will also be discussed. Rapid

changes of ICE during ELMs and sawteeth may provide insight into the fast evolution of the

beam ion distribution due to these instabilities. The two methods of ICE detection used on DIII-

D are also being compared and have so far only shown small differences.

Work supported by US DOE under DE-FC02-04ER54698.


22

I-11: Particle transport due to the nonlinear phase of energetic-particle-driven geodesic

acoustic modes in full-f gyro-kinetic simulations

D. Zarzoso

Aix-Marseille Université, CNRS, PIIM, UMR 7345 Marseille, France


Energetic particles naturally exist in a tokamak due to either fusion reactions or external heating

such as ICRH or NBI. These energetic particles need to be well-confined in order to transfer

their energy to thermal particles and achieve this way a regime with self-sustained fusion

reactions. However, energetic particles excite modes that tend to de-confine the particles

themselves. This is the reason why energetic particle mode excitation and saturation need to be

understood and controlled. We focus our analysis on a special class of energetic particle modes,

called energetic geodesic acoustic modes (EGAMs) [1,2], which have already been analysed in

gyro-kinetic simulations [3]. It was recently observed that these modes can interact with

turbulence, increasing the transport [4] and modifying turbulence properties including how non-

axisymmetric and axisymmetric modes interact [5]. However, so far little work has been done

regarding the radial transport of particles due to EGAMs in the absence of turbulence. The main

reason is that EGAMs are axisymmetric modes and therefore they are believed not to contribute

much to the radial transport of both thermal and energetic particles. In this work, we present for

the first time highly resolved full-f global gyro-kinetic 2-species simulations using GYSELA

code [6] that evidence the formation of chain of islands in phase space during the nonlinear

saturation of EGAMs. Those islands appear at the predicted positions using linear and nonlinear

wave-particle interaction theory. Scans on energetic ion species (charge and mass) and on the

energetic ion fraction have been performed. Three main results have been obtained. First, when

increasing the drive of EGAMs, the width of the islands is enlarged and they can interact with

each other increasing this way the nonlinear damping of the mode. Second, by means of a test-

particle tracing method we solve the particle equations of motion using the self-consistent

electrostatic potential obtained from 2-species GYSELA simulations and show that the EGAM

island can interact strongly with the trapping/de-trapping region characteristic of toroidal

devices. In particular, barely passing thermal particles can be trapped and eventually de-

confined if the drive of EGAM is below a threshold. When the drive of the EGAM is enhanced

barely co- (resp. counter-) passing particles can be first trapped and detrapped afterwards

resulting in counter- (resp. co-) passing particles. Finally, energetic particles far from the

trapping/de-trapping region can be accelerated by the main EGAM island, resulting in larger

orbit widths and increasing their vertical drifts. Additional analysis of the confinement of the

different classes of particles (thermal vs. energetic, co- vs. counter-passing and passing vs.

trapped) is also presented.

References:

[1] R. Nazikian et al, Phys. Rev. Lett. 101, 185001 (2008)

[2] G. Fu, Phys. Rev. Lett. 101, 185002 (2008)

[3] D. Zarzoso et al., Phys. Plasmas 19, 022102 (2012)

[4] D. Zarzoso et al, Phys Rev Lett 110, 125002 (2013)

[5] D. Zarzoso et al, Nucl. Fusion 57 (2017) 072011

[6] V. Grandgirard et al, Comput. Phys. Commun. 207 35-68 (2016)


23

I-12: Transport of confined fast ions in the presence of RMP’s and MHD-induced

perturbations in ASDEX Upgrade

A.S. Jacobsen1, B. Geiger

1, P. Lauber

1, M. Weiland

1, A.J. van Vuuren

1, A. Bock

1, R. Fischer

1,

L. Giannone1, E. Poli

1, M. Reich

1, P. Schneider

1, M. Salewski

2, G. Tardini

1,

the ASDEX Upgrade Team1 and the EUROfusion MST1 Team

1Max-Planck-Institut für Plasmaphysik, Garching, Germany

2Technical University of Denmark, Department of Physics, Kgs. Lyngby, Denmark


The recent improvements of the fast-ion diagnostic system at ASDEX Upgrade make systematic

studies of the fast-ion confinement in NBI and ICRH heated plasmas possible. In particular, the

fast-ion Dα (FIDA) spectroscopy system at ASDEX Upgrade has been upgraded to six optical

heads featuring different viewing directions. This allows one to perform fast-ion velocity-space

tomographies where data from the different spectra are analyzed together. In addition, an

improved motional stark effect diagnostic, a new diamagnetic loop measurement and a neutron

spectrometer give a solid basis for fast-ion transport studies.

During low-density plasmas with substantial off-axis NBI heating power and counter ECCD,

elevated q-profiles with qmin > 2 have been obtained, see figure 1. Here, q=2 sawtooth-like

crashes and continuous TAE’s have been observed for the first time in the flat-top phase of

ASDEX Upgrade discharges, as shown in figure 2. The effect of the q=2 sawtooth-like crashes

and of the TAE’s on the fast ions are investigated and compared to modelling results from

HAGIS/LIGKA.

In addition, the transport caused by RMP’s of fast ions injected by off-axis NBI has been

investigated. During off-axis NBI, measurements of the fast-ion confinement show clear

discrepancies with neoclassical expectations. Measurements from a newly installed edge-FIDA

spectrometer will be compared with 3D modelling using VMEC equilibria. Very strong

discrepancies between neoclassical predictions and measurements have also been observed

during NTM activity. It is found that particularly locked 2/1 NTMs reduce the fast-ion density in

the plasma significantly compared with the purely neoclassical simulation results from

TRANSP. The agreement between simulation and measurement improves when so-called

anomalous fast-ion diffusion is included in the simulations.

Fig 1. q-profiles showing qmin > 2 Fig 2. Magnetic spectrogram showing

TAE’s in the flat-top phase of an ASDEX Upgrade

discharge.


24

I-13: Symmetry breaking of BAE driven by energetic particle

Z.X. Lu1, X. Wang

1, Ph. Lauber

1, F. Zonca

2

1Max-Planck-Institut f��r Plasmaphysik, Garching, Germany

2C.R. ENEA Frascati - C.P. 65, 00044 Frascati, Italy


The mode structure symmetry breaking such as flux surface averaged parallel or radial

wavenumber ⟨k||⟩ or ⟨kr⟩ is a key concept to demonstrate the non-perturbative effect of energetic

particles on Alfvén eigenmodes (AEs) and to study the interaction between low frequency AEs

and thermal/energetic particles (EPs) [1]. It is also important for estimating the momentum

transport due to its connection to the corresponding off-diagonal components [2]. In this work,

the theoretical method is developed to calculate the symmetry breaking and is applied to the

Beta-induced Alfvén Eigenmode (BAE) problem with comparison to XHMGC simulation

results.

The theoretical method is characterized by global physics and non-perturbative EP response.

The 2D (𝑟, 𝜃) problem is decomposed to two coupled 1D problems both for strongly and

weakly coupled poloidal harmonics with the parallel or radial mode structure chosen as the

lowest order solution respectively. For the strongly coupled case, the Mode Structure

Decomposition (MSD) approach [3] is used with the complex envelope phase variation (θ𝑘) as a

generalized ballooning parameter to include the intensity induced symmetry breaking [4]. For

the weakly coupled case, the central poloidal harmonic is solved first, and then the correction

due to coupling between poloidal harmonics can be obtained order by order.

The theoretical method is applied to study the symmetry breaking of BAE with weakly coupled

poloidal harmonics. The theoretical global analysis identifies the essence of “boomerang”

structures with/without asymmetric tails in poloidal plane as well as the radial and parallel

symmetry breaking. The agreement between the theoretical calculation and XHMGC is

demonstrated. Global effects and non-perturbative EP response are important ingredients for the

symmetry breaking and their effects on EP transport as well as the implications to experimental

observations using ECEI are discussed.

References:

[1] Z. Lin, Y. Q. Liu, H. S. Zhang, and W. L. Zhang. In Proceedings of the 25th International Conference

on Plasma Physics and Controlled Nuclear Fusion Research. IAEA, 2016. Paper IAEA-CN-234/TH/P4-

7.

[2] C. Angioni, Y. Camenen, F.J. Casson, E. Fable, R.M. McDermott, A.G. Peeters, and J.E. Rice. Nucl.

Fusion, 52(11):114003, 2012.

[3] Z. X. Lu, F. Zonca, and A. Cardinali. Phys. Plasmas, 19(4):042104, 2012.

[4] Z.X. Lu, E. Fable, W. Hornsby, C. Angioni, A. Bottino, Ph. Lauber, and F. Zonca. Phys. Plasmas,

24(4):042502, 2017.

[5] Z. X. Lu, X. Wang, Ph. Lauber, F. Zonca, Mode structure symmetry breaking of energetic particle

driven Beta-induced Alfvén Eigenmode, Phys. Plasmas, to be submitted.


25

O-1: Fast-ion profiles in discharges with Alfvén eigenmode activity

D.J. Lin1, C.S. Collins

2, W.W. Heidbrink

1, J. Huang

3, D.C. Pace

2, M. Podestà

4,

M. Van Zeeland2, and the DIII-D Team

1University of California Irvine, Irvine, CA 92697, USA

2General Atomics, PO Box 85608, San Diego, CA 92186-5608, USA

3Institute for Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui, China

4Princeton Plasma Physics Laboratory, PO Box 85608, San Diego, CA 92186-5608, USA


In DIII-D, Alfvén eigenmode (AE) activity has been observed to cause significant fast-ion

transport above a stochastic threshold that exceeds the linear threshold for AE stability [1].

Above threshold, transport becomes stiff, and fast-ion profiles measured by the fast-ion D-alpha

(FIDA) diagnostic are virtually unchanged despite increased neutral beam drive. In order to

pinpoint the onset of stiff transport, measured fast-ion profiles are compared with predicted

profiles in the absence of AE-induced transport for several different experiments. In one

experiment, multiple toroidal and reversed shear AEs create a hollow fast-ion profile [2].

Simulations with the TRANSP “kick” model that employ measured AE mode structures

successfully reproduce the measurements [2]. In another experiment, the beam voltage is varied

during the discharge at nearly constant beam power [3]. Variations in beam voltage alter the

virulence of AE activity. In a third experiment, FIDA profiles are measured in high βp plasmas

and compared with predicted profiles. Measuring the degree of fast-ion profile redistribution

across a wide parameter regime is important for both transport model development and for

designing scenarios that avoid undesirable AE-induced transport.

References [1] Collins, C.S., Heidbrink, W.W., Austin, M.E., et al., Phys. Rev. Lett. 116, 095001 (2016).

[2] Heidbrink, W.W., Collins, C.S. Podesta, M., et al., Phys. Plasma 24, 056109 (2017).

[3] Pace, D.C., Collins, C.S., Crowley, B., et al., Nucl. Fusion 57, 014001 (2017).

Work supported by U.S. Department of Energy under DE-FC02-04ER54698, DE-FG03-

94ER54271, and DE-AC02-09CH11466.


26

O-2: Alfvén Eigenmodes and Fast Ion Transport in Negative Triangularity DIII-D

Plasmas

M.A. Van Zeeland1, W.W. Heidbrink

2, M. Austin

3, C. Collins

1, X.D. Du

2, V. Duarte

4, A. Hyatt

1,

G. Kramer4, N. Gorelenkov

4, D. Lin

2, C. Luo

5, G. McKee

6, C. Muscatello

1, C. Petty

1,

M. Walker1 and Y.B. Zhu

2, Y. Zhu

5


2University of California at Irvine, Irvine, CA 92697, USA

3University of Texas at Austin, Austin, Texas 78712

4Princeton Plasma Physics Laboratory, PO Box 451, Princeton, NJ 08543-0451, USA

5University of California at Davis, Davis, California 95616, USA

6University of Wisconsin at Madison, Madison, Wisconsin, 53706, USA


The first energetic particle experiments in a tokamak plasma with negative triangularity were

carried out in DIII-D and significant differences in both Alfvén eigenmode behavior as well as

fast ion transport relative to positive triangularity were observed. It is known that shaping can

have a profound impact on MHD, turbulence and particle orbits. Negative triangularity plasmas,

in particular, are the subject of increasing interest due to experimental observations of reduced

turbulence levels and improved confinement relative to similar positive triangularity cases [1].

In DIII-D negative triangularity plasmas heated by ~80 keV neutral deuterium beams, both

reversed shear Alfvén eigenmodes (RSAEs) and toroidicity induced Alfvén eigenmodes (TAEs)

are observed during the current ramp phase. In many cases, beam driven RSAEs and TAEs in

negative triangularity discharges appear as short, several mode cycle, bursts with rapidly

(f/f~10%) downchirping behavior. This is in contrast to positive triangularity cases where such

rapid chirping behavior is far less common in DIII-D plasmas. Interestingly, rapid RSAE

chirping, not that associated with equilibrium induced variations of the natural mode frequency,

is found to occur more readily in negative triangularity and, to a lesser degree, positive

triangularity at rational qmin crossings where internal transport barrier formation and a brief

reduction in turbulence occurs [2]. Measurements of fast ion transport in negative triangularity

using the FIDA modulation approach [3] show the critical radial beam ion density gradient,

above which fast ion transport due to AEs increases rapidly, is higher than that compared to

previous oval discharges. These negative triangularity plasmas exhibit markedly lower

microturbulence levels, providing interesting test-cases for models that predict lower critical

gradient thresholds [4] and possible transition to AE chirping behaviour [5] when background

ITG/TEM turbulence is reduced; a comparison with these models is underway.

References:

[1] Camenen Y, et.al. Nucl. Fusion, 47 510 (2007)

[2] M.W. Shafer, et.al., Phys. Rev. Lett 103 (2009) 075004

[3] Collins, C.S. et al., Phys. Rev. Lett. 116 (2016) 095001

[4] R.E. Waltz and E.M. Bass, Nucl. Fusion 54, (2014) 104006

[5] V.N. Duarte, et.al. Nucl. Fusion 57 (2017) 054001

This work was supported by the US Department of Energy under DE-FC02-04ER-54698, DE-

FG03-94ER54271, DE-FG02-08ER54984, DE-AC02-09CH11466, DE-SC0012551, DE-AC05-

00OR22725.


27

O-3: Scenario development for the observation of alpha-driven instabilities in JET DT

plasmas

R. Dumont1, J. Mailloux

2, V. Aslanyan

3, M. Baruzzo

4, C. D. Challis

2, I. Coffey

5, E. Delabie

6,

J. Eriksson7, J. Ferreira

8, M. Fitzgerald

2, L. Giacomelli

9, C. Giroux

2, N. Hawkes

2, P. Jacquet

2,

E. Joffrin1, T. Johnson

10, D. King

1, V. Kiptily

2, B. Lomanowski

12, E. Lerche

12,

M. Mantsinen13,14

, S. Menmuir2, K. McClements

2, S. Moradi

2, M. Nocente

15, A. Patel

2,

H. Patten16

, R. Scannell2, S. Sharapov

2, E. Solano

17, M. Tsalas

18, P. Vallejos

10, H. Weisen

16

and JET contributors*

1CEA, IRFM, F-13108 Saint-Paul-Lez-Durance, France

2CCFE, Culham Science Centre, Abingdon, OX14 3DB, UK

3MIT PSFC, 175 Albany Street, Cambridge, MA 02139, US 4Consorzio RFX, corso Stati Uniti 4, 35127 Padova, Italy

5Dept of Pure and Applied Physics, Queens Uni., Belfast, BT7 1NN, UK

6Oak Ridge National Laboratory, Oak Ridge, Tennessee, US

7Dept of Physics and Astronomy, Uppsala Uni., SE-75120 Uppsala, Sweden

8Instituto de Plasmas e Fusão Nuclear, IST, Universidade de Lisboa, Portugal

9Uni. Milano-Bicocca, piazza della Scienza 3, 20126 Milano, Italy

10Fusion Plasma Physics, EES, KTH, SE-10044 Stockholm, Sweden

11Aalto Uni., P.O. Box 14100, FIN-00076 Aalto, Finland

12LPP-ERM/KMS, Ass. EUROFUSION-Belgian State, TEC partner, Brussels, Belgium

13,14BCS and ICREA, Barcelona, Spain

15Uni. Milano-Bicocca, piazza della Scienza 3, 20126 Milano, Italy

16EPFL, SPC, CH-1015 Lausanne, Switzerland

17Laboratorio Nacional de Fusión, CIEMAT, Madrid, Spain

18FOM Institute DIFFER NL-3430 BE Nieuwegein, The Netherlands

Energetic ions in fusion plasmas may destabilize various instabilities. Among them, Toroidal

Alfvén Eigenmodes (TAEs) can be made unstable by the alpha particles resulting from fusion

reactions, and may induce a significant redistribution of fast ions causing a degradation of the

plasma performance, and possibly particle losses to the first wall. In next-step devices, including

ITER, the potential impact of these alpha-driven TAEs remains to be precisely quantified. It is

therefore essential to prepare scenarios aimed at observing alpha-driven TAEs in a future JET

DT campaign. Recent experiments have been conducted in JET deuterium plasmas with this

objective in mind. The requirements for maximizing TAE drive have made it necessary to

operate in a domain of parameters unexplored since the installation of the ITER-like wall.

Discharges at low density, large core temperatures associated with the presence of ITBs

(Internal Transport Barriers) and characterized by good energetic ion confinement have been

performed. ICRH has been used in the hydrogen minority heating regime to probe the TAE

stability. The consequent presence of MeV ions has resulted in the observation of TAEs in many

instances. The impact of several key parameters on TAE stability could therefore be studied

experimentally. Modelling taking into account NBI and ICRH fast ions shows good agreement

with the measured neutron rates, and has allowed extrapolations to DT plasmas to be performed.

TAE stability calculations have also been compared to experimental results.

* See the author list of “Overview of the JET results in support to ITER” by X. Litaudon et al., accepted for

publication in Nuclear Fusion

28

O-4: Destabilization of counter-propagating Alfvénic instabilities by off-axis, co-current

neutral beam injection

M. Podestà, E. D. Fredrickson and M. Gorelenkova

Princeton Plasma Physics Laboratory, Princeton NJ - 08543, USA


Injection of high-energy neutrals (NBI) is a common tool to heat the plasma and drive current

non-inductively in fusion devices. Once neutrals ionize, the resulting energetic particle (EP)

population can drive instabilities that are detrimental for the performance and the predictability

of plasma discharges. A broad NBI deposition profile, e.g. by off-axis injection aiming near the

plasma mid-radius, is often assumed to limit those undesired effects by reducing the radial

gradient of the EP density, thus reducing the “universal” drive for instabilities. However, this

work presents new evidence that off-axis NBI can also lead to undesired effects such as the

destabilization of Alfvénic instabilities, as observed in NSTX-U plasmas. Experimental

observations indicate that counter propagating toroidal AEs are destabilized as the radial EP

density profile becomes hollow as a result of off-axis NBI. Time-dependent analysis with the

TRANSP code, augmented by a reduced fast ion transport model (known as kick model),

indicates that instabilities are driven by a combination of radial and energy gradients in the EP

distribution. The mechanisms for wave-particle interaction revealed by the phase space resolved

analysis are the basis to identify strategies to mitigate or suppress the observed instabilities.

Work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy

Sciences under contract number DE-AC02-09CH11466.


29

O-5: Alpha particle transport due to inelastic collisions

R. Farengo1,3

, C. Clauser2,3

1 Comisión Nacional de Energía Atómica, Centro Atómico Bariloche, Bariloche, Argentina

2 CONICET, Bariloche, Argentina

3 Instituto Balseiro, Bariloche, Argentina

Various mechanisms for anomalous alpha particle transport have been considered. These

include large scale MHD fluctuations, Alfven eigenmodes, microturbulence, toroidal ripple and

perturbations produced by ELM control coils. We have recently showed [1,2] that processes that

change the charge state of the alpha particles, and therefore their Larmor radius, (i. e. charge

exchange) can also produce significant changes in their transport.

A numerical code that calculates the exact alpha particle trajectories and includes elastic and

inelastic collisions was developed. In this code, the probability of charge changing events is

introduced via a Monte Carlo type method while a standard Langevin formulation is used for

classical collisions. The cross sections of the inelastic processes were obtained from the existing

databases. The code runs on a GPU, thus allowing calculations with a large number of particles

in a short time using modest computational resources.

Simulations performed for a realistic ITER-like equilibrium show that charge changing

processes can produce significant changes in the transport of alpha particles in the edge-SOL

region [2]. The addition of inelastic collisions actually reduces the alpha particle loss rate below

the level obtained when only elastic (Coulomb) collisions are included. This is due to the inward

flux produced by the neutral density gradient. Power losses, on the other hand, remain at

approximately the same level because the average energy of the lost particles is higher when

inelastic collisions are included. The spatial distribution of the lost particles changes

significantly when inelastic collisions are added, with a larger fraction of the lost particles

reaching the wall.

We are currently investigating the possibility of validating our model by performing

experiments in existing devices. One possibility would be to inject a helium beam of

approximately 80 keV in an existing tokamak and follow the trajectories of the resulting He

ions. An ionization package has been added to the code for these calculations, to determine the

initial position and velocity of the He ions generated by the neutral beam. Preliminary results

show the same qualitative differences observed in Ref. [2] between the calculations performed

with, and without, including inelastic collisions. In simulations that only include Coulomb

collisions most lost particles reach the divertor, while in those including both elastic and

inelastic collisions a large fraction of particles reaches the wall.

Another possibility would be to determine the effect of inelastic collisions on the transport of

the He3 ions produced by D-D fusion reactions in high power discharges.

References:

[1] C. F. Clauser and R. Farengo, Phys. Plasmas 22, 122502 (2015).

[2] C. F. Clauser and R. Farengo, Nucl. Fusion 57, 046013 (2017).

30

O-6: Fast-ion losses associated with the RMP applications on KSTAR

Junghee Kima, Tongnyeol Rhee

a, S.I. Lee

a, J.-Y. Kim

b, Y. In

a, A. Loarte

c, K. Shinohara

d,

M.J. Choia, and H. Jhang

a

aNational Fusion Research Institute, Daejeon Korea

bPlasmapp Co. Ltd., Daejeon, Korea

cITER Organization, St.Paul-Lez-Durance, France

dNational Institutes for Quantum and Radiological Science and Technilogy, Naka, Ibaraki,

Japan


Edge magnetic perturbation is one of most promising tools for mitigating or suppressing the

ELMs in the magnetic fusion devices. Although the ELM-induced heat flux on the first wall is

reduced significantly by the well-designed RMP configurations, toroidally localized fast-ion

losses have become significant concerns in the fusion plasma experiments [1,2]. In this

presentation, fast-ion loss behaviors under the representative ELM-mitigation and suppression

experiments on KSTAR using all three RMP coil rows are presented. In particular, localized

fast-ion loss intensity measured by the fast-ion loss detector (FILD) [3] under the ‘intentionally

misaligned’ rotating RMP configuration [4] has been reduced as the ‘degree of de-phasing’

increases. Change in the phase difference between upper-middle and middle-lower coil current

waveforms gives the different poloidal spectra of the perturbation field, hence it produces

different ‘degree of non-conservation’ of the fast-ion canonical toroidal angular momentum.

This result implies optimal misalignment of the RMP coil current is beneficial for ELM

mitigation as well as reduction of localized fast-ion loss. Another distinctive feature of fast-ion

loss has been observed during ELM suppression experiments. It has shown the modulation

(~ tens of Hz) of the fast-ion loss signal even in the absence of ELM spikes. Modulation-like

fast-ion loss has not been observed during ELMy H-mode phase, however in the ELM

suppression phase it is well coincided with small oscillations of the edge parameters such as the

locked-mode coil signal (radial magnetic field strength) and the edge electron temperature.

References:

[1] M. Garcia-Munoz et al., Nucl. Fusion 53, 123008 (2013).

[2] K. Shinohara et al., Nucl. Fusion 52, 094008 (2012).

[3] J. Kim et al., Rev. Sci. Instrum. 83, 10D305 (2012).

[4] Y. In et al., 2016 Fusion Energy Conference, EX/1-3


31

O-7: Likelihood for Alfvénic instability bifurcation in experiments

V.N. Duarte1,2

, N.N. Gorelenkov2, E.D. Fredrickson

2, M. Schneller

2, H.L. Berk

3, G.P. Canal

4,

W.W. Heidbrink5, S.M. Kaye

2, M. Podestà

2, M.A. Van Zeeland

4 and W.X. Wang

2

1Institute of Physics, University of São Paulo, São Paulo, SP, 05508-090, Brazil

2Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ, 08543, United

States of America 3Institute for Fusion Studies, University of Texas, Austin, TX, 78712, United States of America

4General Atomics, San Diego, CA 92186, United States of America

5University of California, Irvine, CA 92697, United States of America


Energetic-particle-driven instabilities can seriously limit the performance of present-day and

next-generation fusion devices. We apply a criterion [1] for the likely nature of fast ion

redistribution in tokamaks to be in the convective or diffusive nonlinear regimes. The criterion,

which is shown to be rather sensitive to the relative strength of collisional or micro-turbulent

scattering and drag processes, ultimately translates into a condition for the applicability of

reduced quasilinear modeling for realistic tokamak eigenmodes scenarios. The criterion is tested

and validated against different machines, where the chirping mode behavior is shown to be in

accord with the model. It has been found that the anomalous fast ion transport is a likely

mediator of the bifurcation between the fixed-frequency mode behavior and rapid chirping in

tokamaks. In addition, micro-turbulence appears to resolve the disparity with respect to the

ubiquitous chirping observation in spherical tokamaks and its rarer occurrence in conventional

tokamaks. In NSTX, the tendency for chirping is further studied in terms of the beam beta and

the plasma rotation shear. For more accurate quantitative assessment, numerical simulations of

the effects of electrostatic ion temperature gradient turbulence on chirping are presently

being pursued using the GTS code.

References:

[1] V. N. Duarte et al, Nucl. Fusion 57, 054001 (2017).


32

O-8: Modeling synchrotron radiation images of runaway electrons

M. Hoppe1, O. Embréus

1, A. Tinguely

2, R. Granetz

2, T. Fülöp

1

1

Department of Physics, Chalmers University of Technology, Göteborg, Sweden

2 Plasma Science and Fusion Center, Massachusetts Institute of Technology,Cambridge MA,

USA


One of the most powerful means of studying runaway electrons in tokamaks is by measuring the

synchrotron radiation they emit. In many current experiments, visible light and IR cameras are

used to study the synchrotron radiation spot, and spectrometers measure the synchrotron

radiation spectrum. Due to the strong dependence on the particle energy, pitch angle and radial

position in both the synchrotron spot and spectrum, these can be used to extract valuable

information about the runaway electron distribution function.

Obtaining accurate information about the runaway electron distribution function from

synchrotron radiation measurements however, requires both the magnetic field, camera location

and camera spectral range to be handled properly and taken into account. In this contribution we

present the synthetic synchrotron diagnostic SOFT (Synchrotron-detecting Orbit Following

Toolkit) [1] which simulates the synchrotron radiation from a population of runaway electrons

whose energy, pitch angle and radial location are known in the outer midplane. By following the

guiding-center orbits of the population, effects arising due to the inhomogeneity of the magnetic

field are incorporated, which we show have significant effects on both the synchrotron radiation

spot and spectrum.

As an application of SOFT, we try to reproduce a synchrotron image from one discharge in the

Alcator C-Mod tokamak [2]. By taking measured parameters of the Alcator C-Mod discharge, a

distribution function is obtained with the Fokker-Planck solver CODE [3, 4], for which the

emitted synchrotron radiation can then be simulated in SOFT, which shows good agreement.

With SOFT, an interpretation for the synchrotron radiation spot observed in experiment can be

given, and the characteristic comet shape of the Alcator C-Mod synchrotron radiation spot is

shown to be the result of the vertical placement of the camera, together with the narrow set of

pitch angles possessed by the particles, as well as their radial distribution.

References:

[1] M. Hoppe, MSc Thesis, Chalmers University of Technology (2017).

[2] A. Tinguely, R. Granetz and A. Stahl, 58th Annual Meeting of the APS Division of Plasma Physics.

TO4.00007 (2016).

[3] M. Landreman, A. Stahl and T. Fülöp, Comp. Phys. Comm. 185, 847 (2014).

[4] A. Stahl et al., Nucl. Fusion. 56, 112009 (2016).


33

O-9: Investigation of runaway electron dissipation in DIII-D using a gamma ray imager

A. Lvovskiy1, C. Paz-Soldan

2, N.W. Eidietis

2, D. Pace

2, D. Taussig

2

1Oak Ridge Associated Universities, Oak Ridge, TN, USA

2General Atomics, San Diego, CA, USA


We report the findings of a novel gamma ray imager (GRI) to study runaway electron (RE)

dissipation on the DIII-D tokamak. RE generated by tokamak disruptions could pose a serious

threat to plasma facing components in the case of localized impact to the wall. Strong RE

currents must be mitigated in ITER and future large tokamaks. Realization and optimization of

such a reliable scheme requires development of theoretical models and their experimental

validation on present-day tokamaks.

The GRI measures the bremsstrahlung emission produced by RE collisions with background

ions to provide spatially resolved measurement of the RE energy spectrum and RE density. The

GRI consists of a lead pinhole camera illuminating a matrix of BGO scintillation detectors

placed in the DIII-D mid-plane. It is capable of measuring RE energy spectra in the range 1−60

MeV with pulse time resolution of 100 µs. The number of GRI channels was recently doubled

(up to 56) in order to provide better spatial resolution, and additional shielding of detectors was

implemented to reduce un-collimated gamma flux and increase single-to-noise ratio.

Results from recent experiments on RE dissipation in the quiescent regime (QRE) will be

presented. QRE is characterized by slowly changing plasma parameters, the absence of

transients and a low gamma flux which together ease data analysis and interpretation. Under

varying loop voltage, toroidal magnetic field and plasma density, a non-monotonic RE

distribution function has been revealed as a result of the interplay between accelerating electric

field, decelerating synchrotron radiation and collisional damping [1]. A fraction of the high-

energy RE grows forming a bump at the RE distribution function while synchrotron radiation

decreases. An increase in the frequency of collisions reduces the non-monotonic tail and the

energy growth rate of detected gamma particles. The angular and radial gradients of the RE

population increase along with the energy. These data are consistent with theoretical models. A

possible destabilizing effect of Parail-Pogutse and Whistler instabilities on the RE distribution

function will be also discussed.

References:

[1] C. Paz-Soldan et al. Phys. Rev. Lett. 118 (2017)

Work supported by the US Department of Energy under DE-FC02-04ER54698.


34

O-10: Real-time simulations of the NBI fast-ion distribution function

M. Weiland1, R. Bilato

1, R. Dux

1, B. Geiger

1, A. Lebschy

1, F. Felici

2, R. Fischer

1,

M. Reich1, the ASDEX Upgrade team

1 and the Eurofusion MST1 team

1Max-Planck-Institut für Plasmaphysik, Garching, Germany

2Technische Universiteit Eindhoven, Netherlands


Knowledge of the NBI fast-ion distribution function is important for transport analysis and

magnetic equilibrium reconstruction. For sophisticated real-time plasma control, which will be

essential for the success of future fusion devices, this distribution function needs to be known

already during the discharge. Then, the relevant quantities (e.g. heating profiles, current-drive

etc.) can be coupled to real-time transport and equilibrium codes like RAPTOR (Rapid Plasma

Transport simulatOR), which has already been implemented and tested in the discharge control

systems of present-day machines like TCV and ASDEX Upgrade. Several sophisticated models

exist, that can calculate this beam ion distribution in good agreement with experimental data,

such as NUBEAM, SINBAD-SSFPQL or NEMO/SPOT. The high accuracy of these codes has

however to be paid with relatively high numerical efforts, which compromises their use in real-

time applications.

In this contribution, we present a novel code, which is capable of predicting the NBI fast-ion

distribution in real-time. We discuss the approximations which were needed to arrive at this

goal. A strongly simplified beam geometry is used for calculating the beam attenuation.

Although orbit effects during the slowing-down process are neglected, the beam deposition is

averaged over the first fast-ion orbit to include an approximate treatment of finite-orbit-width

effects. The time-dependent solution of the Fokker-Planck equation (2D in velocity) is then

calculated based on analytic expressions. This novel code currently takes ≈25 ms per time step,

assuming that only one CPU is used per beam. Further optimizations and parallelization should

allow to even further decrease the calculation time. Benchmarks are carried out with the more

sophisticated but also much slower NUBEAM code, indicating a good agreement (see fig. 1).

An inclusion of the model in RAPTOR is already in progress. As further outlook, the model

could be extended to simulate also alpha particles from fusion reactions, which will be of great

importance in particular for future devices.

Fig. 1: Benchmark between the real-time model and NUBEAM


35

O-11: Determining the Population of Individual Fast-ion Orbits Using Generalized

Diagnostic Weight Functions

L. Stagner1 & W.W. Heidbrink

1

1University of California, Irvine: Irvine, CA 92697, USA

Due to the complicated and anisotropic nature of the fast-ion distribution function, diagnostic

velocity-space weight functions [1], which indicate the sensitivity of a diagnostic to different

fast-ion velocities, are used to facilitate the analysis of experimental data. When velocity-space

weight functions are discretized, a linear equation relating the fast-ion density and the expected

diagnostic signal is formed. In a technique known as Velocity-space Tomography [2], many

measurements can be combined to create an ill-conditioned system of linear equations that can

be solved using various computational methods [3].

However, when velocity-space weight functions (which by definition ignore spatial

dependencies) are used, Velocity-space Tomography is restricted, both by the accuracy of its

forward model and also by the availability of spatially overlapping diagnostic measurements. In

this work we extend velocity-space weight functions to a full 6D generalized coordinate system

and show how to reduce them to a 3D orbit-space without loss of generality using an action-

angle formulation. Furthermore, we show how diagnostic orbit-weight functions can be used to

infer the full fast-ion distribution function, i.e. Orbit Tomography. Examples of orbit weight

functions for different diagnostics and reconstructions of fast-ion distributions from

experimental data from a voltage sweeping discharge using ~50 FIDA viewing chords are

shown. This work was supported by the U.S. Department of Energy under DE-AC02-

09CH11466 and DE-FC02-04ER54698.

References:

[1] Heidbrink, W. W., et al. "Measurements of fast-ion acceleration at cyclotron harmonics using

Balmer-alpha spectroscopy." Plasma Physics and Controlled Fusion 49 (2007).

[2] Salewski, M., et al. "Measurement of a 2D fast-ion velocity distribution function by tomographic

inversion of fast-ion D-alpha spectra." Nuclear Fusion 54 (2014).

[3] Jacobsen, A.S., Stagner, L., et al. "Inversion methods for fast-ion velocity-space tomography in

fusion plasmas." Plasma Physics and Controlled Fusion 58 (2016).

36

Fig.1 (a) TRANSP fast-ion distribution for

t=0.44, resonant line for n=-11 GAE;

(b) HYM fast-ion distribution from GAE

simulations(t=0.44s); resonant line for n=-

10. Color dots show resonant particles.

O-12: Numerical simulations of GAE stabilization in NSTX-U

E. V. Belova1, E. D. Fredrickson

1, N. A. Crocker

2, and the NSTX-U team

1PPPL, Princeton NJ, USA

2University of California, Los Angeles, California


Beam-driven Global Alfven Eigenmodes (GAEs) were frequently observed on NSTX and

NSTX-U and have been linked with a flattening of the electron temperature profile in the plasma

core [1]. The counter-propagating GAEs were observed in the sub-cyclotron frequency range of

0.1fci up to 0.5fci, driven unstable by a cyclotron

resonance with the beam ions. New experimental

results from NSTX-U have demonstrated that neutral

beam injection from the new beam sources with large

tangency radii deposit beam ions with large pitch

V||/V~1, which can very effectively stabilize all

unstable GAEs [2]. Numerical simulations using the

HYM code have been performed to study the

excitation and stabilization of GAEs in the NSTX-U

shot #204707 right before (t=0.44s) and shortly after

(t=0.47s) the additional off-axis beam injection. The

beam ion distribution function has been chosen to

match the TRANSP data for this shot, with pitch

distribution in the form Fb~ exp[-(λ-λ0(ε))2/Δλ(ε)

2],

where λ=μB0/ε is the pitch parameter, and assuming a

slowing-down distribution in the beam ion energy, ε.

HYM simulations reproduce experimental finding,

namely it is shown that off-axis neutral beam

injection reliably and strongly suppresses all unstable

GAEs. Before additional beam injection, the

simulations show unstable counter-rotating GAEs

with toroidal mode numbers n=7-12, and frequencies that match the experimentally observed

unstable GAEs. Additional of-axis beam injection has been modeled by adding beam ions with

distribution Fadd~ exp[-λ2/Δλa(ε)

2], i.e. with λ0=0, Δλa<Δλ, and about 1/3 of the total beam ion

inventory. The simulations in this case show a complete stabilization of all unstable GAEs (n=7-

12), even for the cases when the HYM calculated GAE growth rates were relatively large

~0.03ci.

References:

[1] D. Stutman, et al., Phys. Rev. Lett. 102, 115002 (2009).

[2] E.D. Fredrickson et al., accepted for publication PRL (2017).

Work supported by U.S. DOE Contracts DE‐AC02‐09CH11466 and DE-SC0011810.

V||/V


37

O-13: Experimental investigation of stability, frequency and toroidal mode number of

compressional Alfvén eigenmodes in DIII-D

S. Tang,1 K.E. Thome,

2 N. A. Crocker,

1 D. Pace

3 and W.W. Heidbrink

4

1University of California, Los Angeles

2Oak Ridge Associated Universities, Oak Ridge, TN

3General Atomics, San Diego, CA 4University of California, Irvine


An experimental investigation in the DIII-D tokamak of the stability of Doppler-shifted

cyclotron resonant compressional Alfvén eigenmodes (CAE), which have 𝜔 ≲ 𝜔𝑐𝑖, has begun

to validate a theoretical understanding and realize the CAE’s diagnostic potential. Additionally,

CAEs potentially play a significant role in energy transport in spherical tokamaks (ST) [NA

Crocker, NF 2013], so the experiment contributes to a predictive capability for temperature

profiles in STs. These modes are excited in tokamaks by energetic ions from neutral beam

heating (and possibly fusion alphas in a burning plasma) [WW Heidbrink, NF 2006]. The

excited frequencies and toroidal mode numbers are a sensitive function of the details of the fast-

ion phase space distribution, making measurements of CAEs via edge magnetic sensing coils a

potentially powerful passive diagnostic for probing the fast-ion distribution [KG McClements,

NF 2015]. Previous investigation of CAEs in DIII-D [WW Heidbrink, NF 2006] showed that the

modes were unstable both in low toroidal field (BT = 0.6 T) discharges, similar to ST plasmas in

the National Spherical Torus Experiment, as well discharges with a higher field (BT ~ 2T) more

typical for DIII-D.

CAE activity was observed using the Ion Cyclotron Emission (ICE) diagnostic. Preliminary

results show CAEs become unstable as BT crosses below a critical threshold in single beam

discharges where BT is ramped from 2.0 T to 1.3 T. [Plasma current is simultaneously ramped

to hold edge safety factor (i.e. q95) fixed]. The threshold is in the range BT ~ 1.7 – 1.9 T for a

set of co-injecting tangential beam (30L) discharges at different densities with injected power of

at least ~ 2.5 MW and voltage of 80 keV. The exact threshold BT increases with increasing

density. This variation is consistent with a threshold of 𝑣𝑏

𝑣𝐴 ~0.9, using total beam velocity and

line averaged density. The frequencies of the CAEs at onset are f ~ 0.6 fci. Both of these results

are consistent with [WW Heidbrink, NF 2006]. Other beams at lesser voltage or power do not

excite CAEs.

The experiment will be used to validate the hybrid-MHD code HYM. The experiment fully

exploits the flexible capabilities of the neutral beam injection system in DIII-D to investigate

mode stability and observed frequencies and toroidal mode numbers over a range of key

parameters including beam direction, beam velocity, beam ion pitch angle, and beam ion

density. A recently developed capability for varying beam power substantially independently of

voltage allows for the separate exploration of beam ion density and beam voltage dependence.

Other key parameters investigated include plasma current, magnetic field, density and safety

factor.

This work was supported by US DOE Grants DE-SC0011810 and DE-FC02-04ER54698.


38

O-14: Fusion neutron production with deuterium neutral beam injection and enhancement

of energetic-particle physics study in the Large Helical Device

M. Isobe1,2

, K. Ogawa1,2

, T. Nishitani1, N. Pu

2, H. Kawase

2, R. Seki

1,2, H. Nuga

1,

E. Takada3, S. Murakami

4, Y. Suzuki

1,2, M. Yokoyama

1,2, M. Osakabe

1,2,

and LHD Experiment Group1

1 National Institute for Fusion Science, Natural Institutes of Natural Sciences, Toki 509-5292,

Japan 2 SOKENDAI (The Graduate University for Advanced Studies), Toki 509-5292, Japan

3 National Institute of Technology, Toyama College, Toyama, 939-8630 Japan

4 Kyoto University, Kyoto, 615-8540 Japan

A deuterium operation in the Large Helical Device (LHD) began in March 7, 2017, in order to

explore a higher-performance regime and to gain a positive prospect toward a helical fusion

reactor. One of the primary research subjects in the LHD deuterium project is to demonstrate

that the confinement capability of energetic ion is relevant to the future burning plasmas in

helical systems. In LHD, because neutrons are primarily produced by beam-plasma interactions

in LHD, neutron diagnostics can be said to be newly extended energetic-particle diagnostics,

and can enhance energetic-particle physics study in LHD. Maximum total neutron emission rate

is expected to be over 1×1016

(n/s) when full power neutral beam injection heating is carried out.

A comprehensive set of neutron diagnostics has been developed toward the deuterium operation,

consisting of ex-vessel neutron flux monitor (NFM), neutron activation system (NAS), vertical

neutron camera (VNC), scintillating-fiber (Sci.-Fi.) detector, neutron fluctuation detector, and -

ray spectroscopy diagnostic. The NFM was in situ calibrated by using an intense 252

Cf source in

November 2016 prior to the deuterium operation. Total neutron emission rate has reached

3.3×1015

(n/s) so far. Neutron emission rate is the highest in an inward shifted configuration and

it tends to decrease as a plasma is shifted outwardly as expected. Beam blip experiments

indicate that neutron decay time after beam turn-off tends to be shorter as ne increases according

to classical slowing-down theory on energetic ions. A rapid drop of neutron rate associated with

recurrent MHD activities are observed, suggesting rapid loss of beam ions. As part of

commissioning, the VNC performance was checked by changing a magnetic axis position of

plasma. Neutron emission profiles clearly change according to magnetic axis positions. A

difference of neutron emission profiles in co-injected and counter-injected phases can be seen

clearly according to orbit characteristics of co- and counter-going beam ions. In addition to

these, we evaluated the triton burnup ratio to study 1 MeV triton behavior by using NAS and a

Sci.-Fi. detector. The triton burnup ratio depends on magnetic axis positions significantly,

increasing as the plasma is shifted inwardly. In this paper, the LHD deuterium project and the

neutron diagnostics on LHD will be overviewed. Also, representative results measured with the

neutron diagnostics in the first deuterium campaign of LHD will be presented.

39

O-15: Escaping alpha-particle monitor for burning plasmas

V.G. Kiptily

CCFE, UK Atomic Energy Authority, Culham Science Centre, Abingdon OX14 3DB, UK


In ITER the first wall power loads resulting from escaping alphas and fast ions will be measured

with infra-red IR cameras. However, for physics studies this is not sufficient as there is a need to

understand the processes causing the losses. A fast ion loss detector, FILD [1], which could

provide energy and pitch-angle resolution of lost -particles, has been accepted for the R&D for

ITER. Similar devices are used on JET, ASDEX-U, DIII-D etc.

This paper presents a diagnostic system for continuous monitoring of -particle losses, GRAM,

gamma-ray alpha-particle monitor. GRAM could be used for measurement of -particles in the

MeV energy range (E > 1.5 MeV) escaping from the burning plasma to the first wall (FW),

including events with extremely high loss rates. The diagnostic is based on the detection of -

rays produced in the nuclear reaction 9Be(,n)

12C [2]. For this purpose, a thick Be-target can be

placed in the vessel, where the alphas are expected to be lost. The escaped alphas strike Be-

target generating 4.44-MeV -rays, if their energy E > 1.5 MeV; -particles with E > 4 MeV

produce also 3.21-MeV gammas. The Be-target is installed in the field of view (FoV) of a

collimated detector which is protected from neutrons and measures the intensities of these -

rays. The calibrated detector can provide absolute values of -particles flux on FW with

temporal resolution depending on intensity of losses in the range E > 1.5 MeV and E > 4

MeV. Gamma-rays produced by alphas pass to the detector through the Be-target/tile and

neutron shielding with minor attenuation. It is important that the detector line of sight (LoS)

does not intersect a region of the plasma with high density of confined fast alphas. An identical

monitor (“blind”), which does not have Be-target in FoV, is needed for the -ray background

monitoring.

To provide high count rate a new architecture of detectors, GRITER, gamma-ray detector for

ITER is proposed. It consists of a stack of thin isolated high-Z fast scintillators with independent

signal readout. Every section of GRITER could operate at count-rate ~ 5x106 s

-1, substantially

exceeding the capability of a single crystal detector of the same size. It is proposed to use a port,

which could be equipped with 2 monitors in a cassette: one for alpha-particle loss measurements

and a “blind” for the -ray background control. Each collimator is filled with neutron attenuator

based on circulating water. The length of the attenuators is variable and could be controlled by

the level of water depending on the expected fusion power. MCNP calculations show that a

substantial reduction of the -ray background occurs when the monitor LoS does not intersects

carbon materials.

The alpha-particle loss modelling has been carried out with Fokker – Plank codes [3].

During the non-DT operation, GRAM could be available for measurements of escaped DD

fusion products, neutral beam heating D-ions, ICRF accelerated H- and 3He-ions through the

detection of gamma-rays resulting from the reactions 9Be(p,)

10B,

9Be(p,)

6Li,

9Be(d,n)

10B,

9Be(d,p)

10Be,

9Be(t,n)

11B,

9Be(

3He,p)

11B,

9Be(

3He,n)

11C.


40

References:

[1] Veshchev E. A. et al Fusion Science and Technology 61 (2012) 172-184

[2] Kiptily V. G. et al Fusion Technology, 22 (1992) 454-460

[3] Yavorskii V et al J Fusion Energy 34 (2015) 774–784

This work has received funding from the RCUK Energy Programme [grant No EP/P012450/1].

To obtain further information on the data and models underlying this paper please contact

[email protected] .


41

O-16: Excitation and suppression of trapped-energetic-ion driven resistive interchange

modes in LHD plasmas with intense deuterium beam injection

S. Ohdachi1,2

, T. Bando2, M. Isobe

1,2, K. Nagaoka

1, Y. Suzuki

1,2, X. D. Du

3, K. Y. Watanabe

1,

H. Tsuchiya1, T. Akiyama

1, K. Ogawa

1,2, T. Ido

1, A. Shimizu

1, Y. Narushima

1,2,

M. Yoshinuma1,2

, R. Seki1,2

, H. Takahashi1,2

, S. Sakakibara1,2

, K. Toi1, M. Osakabe

1,2,

T. Morisaki1,2

, and the LHD Experiment Group1

1

National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Japan

2 SOKENDAI (The Graduate University for Advanced Studies), Toki, Japan

3 University of California, Irvine, CA, USA


The plasma of the Large Helical Device (LHD), which is L=2/M=10 Heliotron type device, is

intensively heated by the three tangentially injected neutral beams (NBIs) and two

perpendicularly (PERP-) injected NBIs. Perpendicularly injected energetic ions are easily

trapped in the helical magnetic-field-ripple of LHD. It was found that when the precession

motion of trapped energetic particles (EP) interact with the resistive interchange mode, so-called

trapped-energetic-ion driven resistive interchange mode (EIC) is destabilized [1]. Recently, the

NBI system is upgraded and the deuterium beams instead of hydrogen beams are injected. The

acceleration voltage of the two PERP-NBIs is thereby increased from 40kV to 60 / 70KV. It is

expected that the amount of the trapped EPs is increased significantly.

The EICs appear when the line averaged electron density is smaller than about 1.5 x 1019

m-3

.

This condition is similar to the one observed in the hydrogen experiments. Bursts of the

magnetic fluctuation of EIC are observed less frequently, whereas the amplitude of each bursts

is 2~5 times larger than that observed with the hydrogen NBIs. After the large burst of the

magnetic fluctuation, chirping-down of the m/n=1/1 mode localized at the = 1 surface is

observed. Initial frequency of the mode is higher than that with hydrogen NBIs and is about the

precession frequency of the deuteron from the PERP-NBIs. Since the effects of the EIC on the

EPs and the bulk plasmas are quite large [2], we try to control the EIC using m/n = 1/1 resonant

magnetic field perturbation (RMP). When the EIC is marginally unstable, the EICs are

suppressed with the RMP. The suppression / mitigation of the EIC is observed only when the

external field does penetrate the LHD plasma.

References:

[1] X. D. Du, et. al., Phys. Rev. Lett. 114 (2015), 155003.

[2] T. Bando et.al., “Effects of Trapped Energetic Ion Driven Resistive Interchange Modes on Deuterium

Beam Ions and Background Plasmas of LHD”, this meeting.


42

O-17: Characterization of the edge magnetic turbulence during TCV NBH discharges

D.Testa1, A.Iantchenko

2, L.M.Perrone

1, A.Tolio

3, B.Geiger

4, C.Hopf

4, and the TCV

and EUROfusion MST1 teams

1 Swiss Plasma Center, Association EURATOM – Confédération Suisse, EPFL, Lausanne, CH

2 Chalmers University of Technology (SW), exchange student with SPC-EPFL, Lausanne, CH

3 Politecnico di Milano (IT), exchange student with SPC-EPFL, Lausanne, CH

4 Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany

We have extended the mathematical framework developed for the statistical analysis of solar

wind data to the measurement of the magnetic turbulence on the TCV tokamak, taking

advantage of its great operational flexibility and its very large array of magnetic sensors (203

Mirnov coils, with up to 500kHz acquisition frequency, and 3 LTCC-3D coils with a 2MHz

acquisition frequency). In this work we present the results of our analysis for a set of NBH

experiments aimed at assessing the role of turbulence for fast ion confinement and the ensuing

current drive generation.

We use various metrics for the EM turbulence analysis: auto- and cross-correlation spectra,

power spectral density (PSD), probability density function of temporal increments, temporal

structure function, permutation entropy and complexity, fractional Brownian motion (fBm)

statistics. We then determine the Hurst exponent H and fractal dimension D at different scales

using a power law for the temporal structure function and the rescaled range approach. Finally,

we find empirical diffusion coefficients due to magnetic turbulence measured at the plasma edge

by magnetic sensors.

The edge EM turbulence measured during this set of TCV NBH discharges follows remarkably

well the fBm description of the solar wind with 0.1<H<0.4, thus corresponding to negatively

correlated temporal increments and D close to the topological dimension of the system. The

(de-)correlation time is in the sub-msec range, the (de-)correlation length is comparable to

the extent of the probe’s array (toroidal and poloidal), thus the expected propagation velocity of

the turbulent flow U=/>10km/sec, which is comparable to the ion sound speed at the plasma

edge for the toroidal flow, and approaches the Alfvén speed for the poloidal flow. The ensuing

EM diffusion coefficients DEM(UB/B)2[0.1-2.0]m

2/sec are consistent with TRANSP

simulations of the NBH power deposition and FIDASIM analysis of the measured FIDA data.

Using the Taylor hypothesis to link frequency and wavenumber spectra, the PSD is close to the

Kolmogorov scaling PSD~k-5/3

up to ~200kHz, then changes to close the Hall scaling PSD~k-7/3

up to ~600kHz, and further changes up to 1MHz to a PSD~k-4

scaling, likely to be consistent

with EM turbulence damping on electrons.


received funding from the Euratom research and training program 2014-2018 under grant

agreement number 633053. The views and opinions expressed herein do not necessarily reflect

those of the European Commission. This work was supported in part by the Swiss National

Science Foundation.

43

O-18: Collective phenomena in the advanced, beam-driven FRC

R. M. Magee, A. Necas, R. Clary, M. C. Thompson, T. Roche, S. Korepanov, T. Tajima,

and the TAE Team

Tri Alpha Energy, Inc., P.O. Box 7010, Rancho Santa Margarita, CA 9268

The C-2U plasma [1] is a unique fast ion environment. Tangential beam injection into a

relatively modest magnetic field results in fast ion orbits that sample both a high beta field-

reversed configuration (FRC) plasma and a low beta mirror plasma in a single period. The

neutral beam power density (total injected neutral power over FRC volume) is 10x larger than in

large tokamaks, but the fast ion density does not appear to be instability-limited. This is likely

because the near unity ratio of the fast-ion orbit radius to the minor radius of the plasma

inoculates the fast ions against the detrimental effects of high-k instabilities. Multiple

measurements indicate that the fast ion beta approaches, and perhaps even surpasses, the thermal

beta.

The uniqueness of this plasma-fast ion system supports unique energetic particle modes.

Measurements of magnetic fluctuations at the edge of the plasma reveal that there at least three:

a low frequency, chirping mode, an ion cyclotron mode, and a high frequency compressional

Alfvén mode. Remarkably, none of these are observed to have a deleterious effect on global

plasma confinement (again, likely due to the stabilizing effect of the large orbit particles). In

fact, the cyclotron mode has the beneficial effect of dramatically enhancing the DD fusion

reaction rate by channeling energy from the fast particles to the plasma ions on a sub-collisional

timescale.

In this presentation, we experimentally characterize the energetic particle modes in the C-2U

FRC with data from multiple diagnostics including magnetics, interferometry, neutral particle

analyzers and fusion product diagnostics. Results are compared to a particle-in-cell simulation

in a simplified geometry.

References:

[1] M.W. Binderbauer et al., AIP Conference Proceedings 1721, 030003 (2016).

44

O-19: Suppression of Alfvénic modes through modifications of the fast ion distribution

E. D. Fredrickson, E. V. Belova, N. N. Gorelenkov, M. Podestà

and the NSTX-U team

PPPL, Princeton NJ

Compressional and Global Alfvén eigenmodes (CAE and GAE) were common on NSTX in the

frequency range from 0.3MHz up to 2.5MHz. Strongly bursting GAE were correlated with fast

ion transport and a broad frequency spectrum of strong CAE and GAE activity was correlated

with a flattening of the core electron temperature profile. Two of the explanations for this core

Te flattening included enhanced electron thermal transport or a form of beam ion energy

channeling, both due to strong GAE/CAE activity. The NSTX team is studying ways to suppress

beam driven instabilities. It was possible to completely suppress GAE activity with HHFW,

although it required >≈2 MW of HHFW power to suppress the GAE excited with 2MW of beam

injection. Also, application of magnetic perturbations was found to modify Alfvénic wave

activity. A new result from NSTX-U is that injection of any of the new beam sources, which

have tangency radii larger than the magnetic axis, suppress GAE activity. Experiments so far

have shown complete suppression of GAE with 20% - 30% of the beam power in the stabilizing

sources, although careful scans have not been done. Simulations of beam deposition and

slowing down with the TRANSP code have found that these new sources deposit fast ions with

pitch 0.9 < V||/V < 1. This observation is qualitatively consistent with the theory of resonant

drive for these modes [1], which predicts that fast ions with 0 < kL< 2 are stabilizing, and for

2 < kL< 4 are destabilizing. That is, fast ions with V||/V > 0.9 will have relatively small V,

and thus small L. Estimates of these parameters bear out this qualitative prediction. These

predictions based on the local analytic theory are supported by simulations with the HYM code,

which accurately predicts the unstable modes and their frequencies prior to, and predicts their

stability following, the off-axis beam injection. This provides a potentially useful tool for more

careful study of the effect of GAE on core Te flattening, and possibly on anomalous electron

thermal diffusion in general.

References:

[1] Gorelenkov, et al., Nucl. Fusion 43 (2003) 228.

Work supported by U.S. DOE Contract DE-AC02-09CH11466.

45

O-20: Fluid models for burning plasmas: reactive EGAMs

M. J. Hole1, M. Fitzgerald

2, Z. S. Qu

1, B. Layden

1, G. Bowden

1, R. L. Dewar

1

1Research School of Physics & Eng. Australian National University, ACT 0200, Australia

2 EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxfordshire, OX14

3DB, UK


In this work we highlight recent ANU research in energetic particle physics. Topics include (1)

the inclusion of anisotropy and flow into tokamak equilibria, stability and wave-particle

interaction studies [1-2], (2) the calculation of energetic geodesic acoustic modes (EGAMs)

using fluid theory [3], (3) the development and implementation of continuum damping in 3D [4-

5], and (4) the application of these tools to KSTAR, MAST and DIIID discharges. A common

feature of the approaches adopted is the use of fluid theory, or generalized MHD, to capture the

physics of energetic particles.

Our feature example is EGAMs: axisymmetric energetic particle modes found in toroidally

confined plasmas resulting from the geodesic curvature of magnetic field lines. They are

experimentally observed at half of the conventional GAM frequency and are localized at the

core, where there is a significant fast particle population. Until recently, it was widely believed

that EGAMs are driven unstable by a positive gradient of the fast particles in the velocity space.

However, unlike previous studies which treat fast ions kinetically, we consider the thermal ions

and fast ions as different type of fluids with a super thermal flow speed for the latter.

Surprisingly, the frequency and growth rate predicted by our fluid model [5] agree well with the

kinetic theory when the fast ion energy width is small, despite the absence of inverse Landau

damping in the fluid model. This indicates the reactive nature of this instability. Further

investigation reveals the similarity of our reactive EGAMs to the well-known two-stream

instability.

We have also determined the radial structure of the reactive EGAM [6]. We have solved the

resulting dispersion relationship, a second order ODE, both analytically in restricted cases and

numerically in general. It is found that the reactive EGAM global mode structure is formed

with the inclusion of fast ion finite drift orbit effects. In two cases with typical DIII-D

parameters but different q profiles, the global EGAM frequency is slightly higher than the local

EGAM extremum, located either on axis with a monotonic shear or at mid-radius with a

reversed shear. The mode wavelength roughly scales with Lorbit in the core and Lorbit at the edge,

though the dependency is more complicated for the reversed shear case when Lorbit < 0.06a (Lorbit

is the fast ion drift orbit width and a the minor radius). Finally, the growth rate of the global

mode is boosted by 50% to 100% when switching from co-beam to counter-beam, depending on

the fast ion density, which may help to explain the more frequent occurrence of EGAMs with

counter-injection in experiments.

References:

[1] M. Fitzgerald, M. J. Hole, Z. S. Qu, Plasma Phys. Control. Fusion 57 (2015) 025018

[2] M. Ftizgerald, L. C. Appel, M. J. Hole, Nucl. Fusion 53 (2013) 113040

[3] Z. S. Qu, M. Fitzgerald, M. J. Hole, Phys. Rev. Let, Accepted 11/02/2016

[4] G. W. Bowden, M. J. Hole, and A. Könies, Physics of Plasmas 22, 092114 (2015)

[5] G. W. Bowden, A. Könies, M. J. Hole, N. N. Gorelenkov, and G. R. Dennis, Physics of Plasmas 21,

052508 (2014);

[6] Z S Qu, M J Hole and M Fitzgerald Plasma Phys. Control. Fusion 59 (2017) 055018


46

O-21: Nonlinear simulations of chirping geodesic acoustic mode and the associated half-

frequency mode

H. Wang1, Y. Todo

1,2, T. Ido

1, Y. Suzuki

1,2

1National Institute for Fusion Science, Oroshi-Cho 322-6, Toki, Japan

2The Graduate University for Advanced Studies, Oroshi-Cho 322-6, Toki, Japan


The energetic particle driven geodesic acoustic modes (EGAM) in a 3-dimensional LHD

equilibrium data are simulated using MEGA code. MEGA is a hybrid simulation code for

energetic particles interacting with a magnetohydrodynamic (MHD) fluid[1,2]

. The poloidal

velocity oscillation is a combination of m/n = 0/0 (strong), 1/0 (medium) and 2/10 (weak)

components. This is caused by the LHD configuration, different from the tokamak case. The

phenomena of chirping primary mode and the associated half-frequency secondary mode[3]

are

firstly reproduced with the realistic input parameters and 3-dimensional equilibrium, as shown

in figure 1. There are good agreements between simulation and experiment on the frequency

chirping of the primary mode, on the excitation of the secondary mode, on the mode profile, and

on the phase lock. It is found that the bulk pressure

perturbation and the energetic particle pressure

perturbation of the secondary mode are in anti-

phase and cancel out with each other. Thus, the

frequency of the secondary mode is low. Also, in

addition to the nonlinear MHD model, another

simulation model with linearized MHD equations

is developed to clarify the fluid nonlinear coupling

effects on the excitation of the secondary mode. It

is found that the secondary mode can be still

excited with large amplitude although the MHD

equations are linearized. This comparison suggests

that the secondary mode is excited by the energetic

particles, not by the nonlinear MHD coupling. In

addition, energy transfer analysis in phase space

confirms the excitation by the energetic particles.

Reference:

[1] Y. Todo, Phys. Plasma 13, 082503 (2006).

[2] H. Wang, Y. Todo and C. Kim, Phys. Rev. Lett 110, 155006 (2013).

[3] T. Ido, K. Itoh, M. Osakabe et al, Phys. Rev. Lett. 116, 015002 (2016).

Fig. 1 Both the chirping primary mode and

the associated half-frequency mode are

reproduced by MEGA code.


47

O-22: Phase-Space Dependence of Fast-Ion Transport by Neoclassical Tearing Modes

W.W. Heidbrink,1 L. Bardoczi,

2 C.S. Collins,

3 G. Kramer,

4 D. Lin,

1 C. Muscatello,

3 M. Podesta,

4

M. Van Zeeland,3

and Y.B. Zhu1

1University of California, Irvine

2Oak Ridge Institute for Science and Education

3General Atomics

4Princeton Plasma Physics Laboratory


The fast-ion transport caused by neoclassical tearing modes (NTM) in H-mode DIII-D plasmas

is investigated in different parts of fast-ion phase space using the newly developed beam

modulation technique and a variety of fast-ion diagnostics that are sensitive to different parts of

the distribution function. As measured by electron cyclotron emission, the (m,n) = (2,1) tearing

modes have an island width of ~10 cm and change phase 180o at the q = 2 surface. (Here, m is

the poloidal mode number and n is the toroidal mode number.) The fast ions are produced by

deuterium neutral beam injection at 75-81 keV. To measure fast-ion transport in different parts

of phase space, one neutral-beam source is modulated at 20 Hz. Flows in phase space are

obtained through comparisons of measured neutron, solid-state neutral particle analyzer, and

fast-ion D-alpha signals with the expected signals in the absence of wave-induced transport [1].

In order to populate different parts of phase space, on successive discharges, beams with six

different injection geometries are modulated. Initial analysis indicates that the largest transport

occurs for on-axis, tangentially-injected ions, while smaller transport occurs for off-axis or

perpendicular injection. Simulations of tangentially-injected ions with the full-orbit code

SPIRAL [2] predict stochastic orbits for similar conditions. Analytic predictions [3] and

TRANSP “kick” model simulations [4] are also compared with the data.

References:

[1] HEIDBRINK, W. W. et al., Nucl. Fusion 56 (2016) 112011.

[2] KRAMER, G. J. et al., Plasma Phys. Controlled Fusion 55 (2013) 025013.

[3] MYNICK, H. E., Phys. Fluids B 5 (1993) 1471.

[4] PODESTA, M. et al., Plasma Phys. Controlled Fusion 56 (2014) 055003.



48

O-23: Experimental evidence of beam ion acceleration during edge localized modes in the

ASDEX Upgrade tokamak

J.Galdon-Quiroga1, M.Garcia-Munoz

1, K.G.McClements

2, M.Nocente

3, S.Freethy

4, M. Hoelzl

4,

A.S. Jacobsen4, J.F.Rivero-Rodriguez

1, F.Orain

4, M.Salewski

5, L.Sanchis-Sanchez

1, E.Viezzer

1,

the ASDEX Upgrade4

and EUROfusion MST1 Teams*

1Dept. of Atomic, Molecular and Nuclear Physics, University of Seville, Seville, Spain

2CCFE, Culham Science Centre, Abingdon OX14 3DB, United Kingdom

3Dipartimento di Fisica ‘G Occhialini’, Università di Milano-Bicocca, Milano, Italy

4Max Planck Institute for Plasma Physics, Garching, Germany

5Department of Physics, Technical University of Denmark, Kgs. Lyngby, Denmark


Experimental evidence of beam ion acceleration due to edge localized modes (ELM) has been

observed for the first time in the ASDEX Upgrade tokamak. Bursts of enhanced fast ion losses

associated to individual ELM filaments are measured with the fast ion loss detector (FILD) [1]

(Fig.1). Multiple pitch angle structures are observed for different beam sources and q95 values at

well-defined energies above the main neutral beam injection energy in the velocity space of the

lost ions, which is reconstructed by means of tomographic inversion techniques of the FILD

signal (Fig.2). This suggests that the acceleration results from a resonant interaction between the

beam ions and the parallel electric field generated during the ELM filaments eruption.

Consistent with the FILD measurements, bursts in electron cyclotron emission are observed at

the onset of the ELM as well as in soft X-ray channels with lines of sight tangential to the

plasma edge. These are both indicative of electron acceleration [2], strongly supporting the

hypothesis of a parallel electric field as responsible for the particle acceleration. Full orbit fast

ion simulations have been carried out including the 3D perturbation fields of the ELM modelled

* H. Meyer et al. Nuclear Fusion FEC 2016 Special issue (2017)

Fig.1. Fast-ion filaments measured by FILD

during an ELM. The blue and red curves show the

signals of two FILDs located at different toroidal

positions. The black curve represents the divertor

current signal.

Fig.2. Gyroradius profile of fast ion losses

measured by FILD during an ELM. The blue curve

shows the experimental signal. The red curve

shows the energy components of the tomographic

inversion. The grey, green and pink curves show

the synthetic FILD signal for the different

components. The total synthetic FILD signal is

shown in black.


49

with JOREK. Key experimental observations such as the filamentary pattern in the temporal

evolution of the losses and the ion acceleration via resonances with the parallel electric field can

be reproduced. This finding may shed light to the contribution of fast particles to the ELM

stability as well as the loss of energy and particles during the ELM cycle.

References:

[1]M.Garcia-Munoz et al, Plasma Phys. Control. Fusion 55 124014 (2013)

[2]S.Freethy et al, Phys. Rev. Lett. 114 125004 (2015)

50

O-24: Excitation of Low Frequency Alfven Eigenmodes in Toroidal Plasmas

Zh. Lin

Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA

Low frequency Alfven eigenmodes in toroidal geometry, such as beta-induced Alfven-acoustic

eigenmode (BAAE) and beta-induced Alfven eigenmode (BAE), can cause significant loss of

energetic particles in fusion plasmas. Since BAAE has strong interactions with both thermal and

energetic particles due to its low frequency, it can be excited by either energetic or thermal

particles, and may affect thermal plasma transport. It might also serve as a channel for directly

converting kinetic energy of --particles to thermal ion energy, a potentially favorable operating

scenario for burning plasmas experiment ITER.

The BAAE was first suggested by an ideal magnetohydrodynamic (MHD) theory, which only

predicts a low frequency BAAE gap generated by toroidal coupling of shear Alfven continuum

and ion acoustic continuum. However, the existence of discrete frequency BAAE has never been

predicted by the analytic theory, although discrete frequency modes inside the low frequency

gap have been found by ideal MHD eigenvalue codes. Furthermore, a gyrokinetic theory argued

that strong Landau damping by thermal ions would prevent a significant response to acoustic

polarizations in collisionless plasmas and that a kinetic thermal ion gap is more appropriate to

describe properties of low frequency spectra.

Our global gyrokinetic toroidal code (GTC) simulations find that unstable BAAE and BAE can

be simultaneously excited with similar radial mode width and comparable linear growth rates

even though the damping rate of BAAE is much larger than BAE in the absence of energetic

particles. This surprising result is attributed to non-perturbative effects of the energetic particles

that modify ideal MHD mode polarizations and nonlocal geometry effects that invalidate

radially local acoustic dispersion relation. In fact, simulation results show that unstable BAAE

and BAE both have dominant Alfvenic polarizations for poloidal sidebands. On the other hand,

the damped BAAE has dominant acoustic sidebands while the damped BAE has dominant

Alfvenic sidebands. Direct calculations of wave-particle energy exchanges show that thermal

ion Landau damping of the unstable BAAE is very weak (at a level similar to the BAE

damping) due to the fact that the sidebands are dominated by Alfven polarizations and that the

local acoustic dispersion relation is not valid for radially broad mode structure of the unstable

BAAE. These simulation results indicate that non-perturbative and radially nonlocal theory are

required for properly describing the excitation of BAAE. Finally, GTC simulations with various

tokamak sizes show that dominant mode changes from the BAAE in a larger tokamak to the

BAE in a smaller tokamak due to the dependence of wave-particle resonance condition on the

tokamak size.

In nonlinear GTC simulations, a beat wave (sum of BAE and BAAE frequency) is excited in the

case where linear BAE and BAAE instabilities co-exist. Amplitudes of BAE, BAAE, and beat

waves oscillate, indicating nonlinear transfers of spectral energy. In the case dominated by linear

BAAE instability, BAAE frequency chirps down during the nonlinear stage, which is consistent

with EP-BAAE resonance conditions. In the case dominated by, linear BAE instability, the

lower frequency BAAE is nonlinearly driven after BAE saturates, and the BAAE frequency

chirps down. Similar nonlinear generation of BAAE by BAE is also observed in the realistic

simulation of a DIII-D experiment where low frequency Alfven eigenmodes are responsible for

half of the fast ion loss. We note that studies of Alfven eigenmodes have mostly focused on the

51

linear excitation. Our finding of nonlinear BAAE excitation points to another interesting, and

yet largely unexplored, mechanism for exciting low frequency Alfven eigenmodes in fusion

plasmas.

In collaborations with Yaqi Liu, Huasen Zhang, Wenlu Zhang. Work supported by U.S. SciDAC

GSEP Center and by China National Magnetic Confinement Fusion Science Program.

52

AEF10

P-1: NBI wall load simulations in the Wendelstein 7-X stellarator with ASCOT

Simppa Äkäslompolo, Sergey Bozhenkov, Michael Drevlak, Yuriy Turkin, Robert Wolf

and W7-X Team

Max-Planck-Institut für Plasmaphysik, Wendelsteinstraße 1, 17491 Greifswald, Germany

The Wendelstein 7-X (W7-X) is a modular,

optimized helical axis stellarator. The W7-X

neutral beam injection (NBI) systems are currently

being installed and the first experiments are

planned for the 2018 W7-X experiment campaign

OP1.2b.

The W7-X magnetic field is optimized to minimize

the radial drift of trapped particles. However,

detailed numerical studies have shown that the

confinement of trapped fast ions, e.g. many NBI

ions, is far from ideal (Drevlak, Geiger, Helander,

& Turkin, 2014). The power and particle load from

the escaping fast ions may heat up and damage the

plasma facing components (PFCs), especially the

stainless steel panels which during OP 1.2b will

not be water cooled.

This contribution presents wall load calculations performed with the ASCOT suite of codes

(Hirvijoki, et al., 2014). The modeling includes the realistic NBI geometry and, for the first

time, a highly detailed 3D wall model (see figure). The load in the 8 reference magnetic

configuration is studied for hot spots on the wall. The high mirror configuration, being the most

promising, is analyzed in a range of plasma scenarios. The modular coil ripple is found to

induce most of the hot spots.

The wall loads are found to be high enough to call for remedial measures. These include

specially designed magnetic configurations that reduce the load to steel components as well as

monitoring of the PFCs with cameras and the impurity flux with spectrometers. The OP1.2b

experiments will show if e.g. the first wall needs additional armoring for later campaigns (OP2)

starting in 2020.

References:

[1] Drevlak, Geiger, Helander and Turkin, "Fast particle confinement with optimized coil currents in the

W7-X stellarator," Nuclear Fusion, 2014.

[2] Hirvijoki, Asunta, Koskela, Kurki-Suonio, Miettunen, Sipilä, Snicker and Äkäslompolo, "ASCOT:

Solving the kinetic equation of minority particle species in tokamak plasmas," Computer Physics

Communications, 2014.


received funding from the European Union’s Horizon 2020 research and innovation programme

under grant agreement number 633053. The views and opinions expressed herein do not

necessarily reflect those of the European Commission

Fig. 1. An example of the calculated wall

loads near the port AEF10 in the high mirror

configuration. The color indicates the heat

load on logarithmic scale.

53

P-2: IC emission in NBI and ohmically heated plasmas in TUMAN-3M tokamak

L.G. Askinazi, A.A. Belokurov, D.B. Gin, V.A. Kornev, S.V. Lebedev, A.E. Shevelev,

A.S. Tukachinsky, N.A Zhubr

Ioffe Institute, 194021, St.-Petersburg, Russian Federation


Ion cyclotron (IC) resonance is a fundamental phenomenon essential for different types of

plasmas ranging from interstellar to laboratory scales. In fusion research, IC heating is

considered as one of the most powerful methods of plasma heating, whereas IC emission (ICE)

generated by plasma itself might be used as a diagnostic tool to measure ion population

characteristics. While some theoretical background explaining ICE generation does exist, see for

example [1], a clear physical picture of ICE generation in fusion-related plasma is still to be

established.

In this paper we report on ICE observation in the NBI-heated plasma in the TUMAN-3M

tokamak. Experiments were performed in deuterium target plasma, with neutral heating beam

consisting of 60% deuterium and 40% hydrogen accelerated up to 16 keV. High frequency

internal magnetic probes were used as a diagnostic tool for ICE detection. With some delay after

NBI pulse front, emission with 13MHz frequency was observed; this frequency corresponds

approximately to fundamental IC resonance for hydrogen near the magnetic axis. Second and

third harmonics were observed as well, though their amplitudes were much lower. No IC

resonance existed for deuterium in TUMAN-3M plasma in this experiment. Spectral analysis

revealed fine structure of the fundamental line, with strong high- and low-frequency satellites

shifted asymmetrically from a weaker central line by 0.1 and 0.2 MHz, respectively. All three

components were found to be rather narrow, of approximately 50kHz FWHM. When target

plasma main species and neutral beam composition were switched to mainly hydrogen, with

some fraction of deuterium in NB still present, the observed magnetic oscillation frequency has

changed to approximately 6.5 MHz, which is close to central IC resonance for deuterium.

However, fine structure of deuterium ICE line in hydrogen plasma was not observed. In the both

cases, the observed frequency was set by fast minority ions injected into target plasma with

neutral heating beam. Moreover, when concentration of these ions increased up to a certain level

due to the fast ion accumulation during NBI shot, and these ions became minority no more, the

IC emission gradually decreased, indicating the importance of low fraction of the minority. In

pure ohmic heating regime, ICE was observed as well, however with quite different properties.

This rather weak emission was observed at up to 7th

harmonics of IC of main ions, both in

deuterium and hydrogen plasmas. These frequencies correspond to resonant condition in the

close proximity to the probes’ location, and, as such, are different in LFS and HFS of the torus.

As energetic ions are normally absent in ohmicaly heated plasma, there must exist some other

source of free energy required for excitation of these oscillations. That might be, according to

[1], density gradient or non-equilibrium ion distribution function.

References

[1] A.B. Mikhailovsky, Nucl. Fusion, 11(1971), 323

The study was supported by Russian Science Foundation (Project # 16-12-10285) and by Ioffe

Institute.


54

P-3: Excitation of energetic particle driven Geodesic Acoustic Modes (EGAMs) by the

velocity anisotropy of ion beam with slowing down and Maxwellian distribution

I. Chavdarovski1, M. Schneller

2, Z. Qiu

3 and A. Biancalani

1

1Max-Planck-Institut fur Plasmaphysik, 85748 Garching, Germany;

2Princeton Plasma Physics Laboratory, P.O.Box 451, Princeton, NJ 08543 USA;

3Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027,PR China;


We derive the local dispersion relation of energetic-particle- induced Geodesic acoustic modes

(EGAMs) for both circulating and trapped particle beam with single pitch angle slowing down

and Maxwellian distribution. Solutions of the local dispersion relation for each case give the

spectrum, the growth rate and the threshold of excitation (if any) as function of the slowing

down critical energy and the pitch angle. Analytical results are benchmarked with simulations

conducted with gyrokinetic PIC code - GTS. The localization and mode structure are examined

numerically depending on the location and peaking of a Gaussian-shaped EP beam.


55

P-4: Development of a Novel Scintillator-Based, Imaging Neutral Particle Analyzer in

DIII-D tokamak

X.D. Du1, W.W. Heidbrink

1, M.A. Van Zeeland

2 and D. Su

2

1University of California at Irvine, Irvine, CA 92697, USA



In the DIII-D tokamak, significant fast ion transport induced by multiple small amplitude Alfvén

eigenmodes (AE) occurs when the beam power exceeds a certain threshold. The threshold value

varies between different energetic particle diagnostics that weight different regions of phase

space. This suggests that an energetic particle flow might be generated in phase space by the

modes. To investigate the flow, a diagnostic system having fine energy and pitch resolution and

well covering the phase space regions where the particle and wave interacts is crucial. Here, we

report the development of a novel compact scintillator-based imaging neutral particle analyzer

in the DIII-D tokamak, referred as an INPA. The primary principle of this measurement is as

follows: the energetic neutrals, born mainly from charge exchange interaction of neutral beams

and background plasma, are collected through a pinhole collimator and are captured by the local

magnetic field after colliding with an ultra-thin (10 nm) carbon stripping foil inside the vacuum

vessel. A phosphor is employed as a magnetic spectrometer to resolve the gyroradii of the

ionized neutrals, which is proportional to the square root of particle energy. In this system, a

wide radial range from plasma core to edge and deuterium energy up to 80 keV are two-

dimensionally imaged with fine resolution. The image is transmitted to a fast-frame camera with

the aid of a telescope system and a narrow band filter. A synthetic diagnostic code including

neutral flux estimation, neutral-foil interaction, orbit tracing and scintillation has been

developed to interpret the experimental data from the INPA. Predictive calculations indicate the

system will have excellent signal to noise and provide unprecedented details of phase space

dynamics and fast ion transport due to instabilities.

References:

[1] C.S. Collins, et.al. Phys. Rev. Lett., 116 095001 (2016)

This work was supported by the US Department of Energy under DE-FC02-04ER-54698, DE-

FG03-94ER54271, DE-FG02-08ER54984, DE-AC02-09CH11466, DE-SC0012551, DE-AC05-

00OR22725.


56

P-5: Resonance frequency broadening of wave-particle interaction in tokamaks due to

collision and microturbulence

G. Meng1,2

, N. N. Gorelenkov2, H. L. Berk

3, V. N. Duarte

4,2, R. B. White

2, A. Bhattacharjee

2

1Peking University, China

2Princeton Plasma Physics Laboratory, USA

3University of Texas, Austin, USA,

4University of São Paulo, Brazil


The resonance width of energetic particles (EPs) and waves, affected by different dissipation

mechanisms and nonlinear effects, is crucial for the understanding and modelling of EP

transport. When there is a perturbation of a single toroidal number n with the ansatz 𝑒𝑥𝑝(𝑛𝜁 −

𝑚𝜃 − 𝜔𝑡), the resonance condition is determined by Ω(𝐸, 𝑃𝜁 , 𝜇) = 𝜔 − 𝑛⟨𝜔𝜁⟩ − 𝑙⟨𝜔𝜃⟩ = 0,

where ⟨𝜔𝜁⟩ and ⟨𝜔𝜃⟩ are the mean toroidal angular and poloidal angular frequency of EPs and 𝑙

is an integer. By considering the mode growth rate 𝛾, scattering rate 𝜈 and finite amplitude, the

width of resonance frequency broadening ΔΩ can be modeled by [1] ΔΩ = 𝑎𝜔𝑏 + 𝑏𝛾 + 𝑐𝜈 ,

where 𝜔𝑏 is the bounce frequency of the most deeply trapped particles by the field, and the

coefficients 𝑎, 𝑏, 𝑐 can be calculated by enforcing the quasilinear evolution for isolated modes to

match the expected analytical levels for single mode saturation[2].

In this work, we use ORBIT to study the broadening of resonance in realistic equilibrium for

DIIID shot 159243[3] and the parametric dependencies of the broadening width on bounce

frequency, growth rate and scattering rate. With only a finite perturbation applied, the

broadening of canonical momentum 𝛥𝑃𝜁 and energy 𝛥𝐸 is inferred from kinetic Poincare plot.

For the case with scattering where the kinetic Poincare plot becomes blurred, the broadening

width is obtained by studying particle redistribution since the resonant island width is the

platform for momentum and energy exchange between particle and waves. It is found that

scattering leads to particle diffusion in phase space and increases resonance broadening

significantly. With perturbation, scattering broadens resonance not only by kicking particles in

and out the primary resonance island but also kicking particle across the adjacent secondary

resonance island region. The redistribution process by mode trapping is much faster than

scattering. The diffusion coefficient is larger at resonance island center than at the edge when

perturbation is small. For DIIID, anomalous stochasticity has more important effect on the

broadening compared to the collisional scattering.

These results will be used to compare with RBQ[4] and NOVA-K for the validation of the

resonance width modelling. This work will help to improve the modelling of the nonlinear

process and EP transport by providing more comprehensive physics ingredients and analyses for

synergistic effects due to different mechanisms.

References:

[1] Berk, H. L., et al., Line broadened quasi-linear burst model. Nucl. Fusion, 1995. 35(12):1661.

[2] Ghantous, K., H. L. Berk and N. N. Gorelenkov, Comparing the line broadened quasilinear model to

Vlasov code. Phys. Plasmas, 2014. 21(3): 032119.

[3] Collins, C.S., et al., Observation of Critical-Gradient Behavior in Alfven-Eigenmode-Induced Fast-

Ion Transport. Phys. Rev. Lett., 2016. 116(0950019).

[4] Gorelenkov, N., V. Duarte and H. Berk. Building 1D resonance broadened quasilinear (RBQ) code

for fast ions Alfvénic relaxations. APS Meeting, 2016.


57

P-6: Resonance line broadened quasilinear (RBQ) code for fast ion Alfvénic relaxations

N. N. Gorelenkov1 , V. N. Duarte

2, M. Podesta

1

1Princeton Plasma Physics Laboratory, Princeton University

2Institute of Physics, University of São Paulo, Brazil

The performance of the burning plasma can be limited by the requirements to confine the super-

alfvenic fusion products, e.g. alpha particles, and the auxiliary heating ions which are capable of

resonating with the Alfvénic eigenmodes (AEs). The effect of AEs on fast ions is evaluated

using the quasi-linear approach [1] generalized for this problem recently [2]. The generalization

involves the resonance line broadened interaction regions with the diffusion coefficient

prescribed to find the evolution of the velocity distribution function. The baseline eigenmode

structures are found using the NOVA-K code perturbatively [3]. The interaction of fast ions and

AEs is captured for the cases where there are either isolated or overlapping modes.

A new code RBQ allowing the diffusion in radial direction (1D) is being built and is presented

here. The wave particle interaction can be reduced to one-dimensional dynamics where for the

Alfvénic modes typically the particle kinetic energy is nearly constant. Hence to a good

approximation the Quasi-Linear (QL) diffusion equation only contains derivatives in the angular

momentum. The diffusion equation is then one dimensional that is efficiently solved

simultaneously for all particles with the equation for the evolution of the wave angular

momentum. The evolution of fast ion constants of motion is governed by the QL diffusion

equations which are adapted to find the ion distribution function.

We make initial applications of the RBQ to DIII-D plasma with elevated q-profile where the

beam ion profiles show the stiff transport conditions [4]. Properties of AE driven fast ion profile

relaxation are studies for validations of the applied QL approach in realistic conditions of beam

ion driven instability in DIII-D.

References:

[1] H. L. Berk, B. N. Breizman, J. Fitzpatrick, M. S. Pekker, H. V. Wong, and K. L. Wong, Phys.

Plasmas, 3, 1827 (1996).

[2] V. N. Duarte, K. Ghantous, H. L. Berk, and N. N. Gorelenkov, Bull. Amer. Phys. Society (abstract

BP8.00037) 59, http://meetings.aps.org/link/BAPS.2014.DPP.BP8.37 (2014).

[3] N. N. Gorelenkov, C. Z. Cheng, and G. Y. Fu, Phys. Plasmas 6, 2802 (1999).

[4] C. S. Collins, W. W. Heidbrink, M. E. Austin, G. J. Kramer, D. C. Pace, C. C. Petty, L. Stagner, M.

A. Van Zeeland, R. B. White, Y. B. Zhu, and The DIII-D team, Phys. Rev. Letters 116, 095001 (2016).

58

P-7: Geodesic modes driven by plasma fluxes during auxiliary NB or ICR heating in

tokamaks

F. Camilo de Souza, A. G. Elfimov, R. M. O. Galvão

Institute of Physics, University of São Paulo, São Paulo, 05508-090, Brazil

The effect of a minor concentration of energetic particles produced by NB injection or ion

cyclotron resonance heating (ICR) on Geodesic Acoustic Modes (GAM) spectrum [1] is

analyzed using fully kinetic equation for large safety factor q>>1. Due to dynamic friction of

energetic particles with electrons vTe> Ven and strong scattering by ions for

beef mTZVV 31

cren 5.5 [2], these particles may have “bump on tail like” distribution

2222

0 2)(exp)(1 Tbcrb vVvF with pitch angle 1 , 1||0 vv for NB

injection or 00 for ICR heating. Using that distribution, it is found that the standard GAM

frequency is reduced by the effective mass renormalization by energetic ions. A new energetic

GAM branch with higher frequency is found for the case when the mode frequency stays near

the bump circulation frequency. The analysis is done using the simplified dispersion equation

0 )1(1102

22

3

for 1 crVRq where 22 )i21(1 crGG V

and the parameter42

2

5

2

crb

b

Vnq

T in the limits 11.0 and. The electron current in

combination with NB driven ion flow [3], modeled by shifted Maxwell distribution, may

overcome the ion Landau damping thus resulting in the GAM instability when electron current

velocity is larger than the effective parallel GAM phase velocity Rq. Similar equation is found

for ICR minority heating. Qualitative agreement of the theory with co/counter NB injection

experiments in COMPASS tokamak [4] is demonstrated.

References:

[1] H. L. Berk et al, Nuclear Fusion 46, S888 (2006).

[2] T.H. Stix, Plasma Physics, v.14 (1972) 367.

[3] A. G. Elfimov, F. Camilo de Souza, R. M. O. Galvão Phys. Plasmas, 22 (2015) 114503.

[4] A. G. Elfimov et al, 43rd

EPS Conference on Plasma Physics 4 - 8 July 2016, Leuven, Belgium,

Europhysics conference abstracts, Vol. 40A, P2.038, 2016.

59

P-8: Lifetime of Runaway Electrons at Phase-space Attractor

Adrian K. Fontanilla, Boris N. Breizman

Institute of Fusion Studies, University of Texas at Austin

E-mails of Corresponding Authors: [email protected], [email protected]

The lifetime of pre-existing runaway electrons in a plasma determines how likely these electrons

will undergo avalanche multiplication. We calculate the lifetime of the fast electrons using the

kinetic equation and include the effects of Coulomb collisions, synchrotron radiation, and

acceleration by the electric field. The lifetime typifies a tug-of-war that occurs between the

thermal bulk of electrons and the attractor that is formed at ultra-relativistic energies. We show

that the rate of thermalization of fast electrons depends on the value of the parameter α =

(Z+1)/(τrad)1/2

(where τrad = τs / τc is the synchrotron time scale normalized to the Coulomb

scattering time scale and Z is the ion charge) compared to the electric field, ε = E/EC

(normalized to the Connor-Hastie critical value). We identify two cases where the rate of

thermalization is slow enough to enable us to transform the kinetic equation into an eigenvalue

problem in which the eigenfunction describes the universal shape of the distribution function

and the eigenvalue represents the lifetime, τℓ. Our eigenfunctions concur with the paper by Guo

et al.[1] In one case, α2 << 1 and the electric field required to sustain the pre-existing runaways

is barely larger than the Connor-Hastie critical value. In the same manner as Aleynikov and

Breizman [2] we make use of the smallness of the electric field to solve the equation

perturbatively but extend the work to demonstrate that the lifetime grows exponentially with the

electric field at a rate that depends on α. Calculations of the lifetime for this case are shown in

the enclosed figure. In the second case, α2 >> 1 and the requisite electric field is much greater

than unity. The largeness of the electric field in this case enables us to universalize the kinetic

equation such that no physical parameters appear in the equation. The equation is then further

reduced to a non-linear ODE via the WKB approximation. We discover than the number of

runaways far from the attractor is exponentially small and conclude that the lifetime of the fast

electrons must therefore be exponentially long.

(a) (b)

Fig. 1: (a) Lifetime versus electric field for various values of the parameter α = (Z+1)/(τrad)1/2

. (b) Contours

of the (log of the) distribution function show fast electrons localized near the attractor, i.e. p = 1.

References:

[1] Z. Guo, C.J. McDevitt, X. Tang Plasma Phys. Control. Fusion 59, 044003 (2017)

[2] P. Aleynikov and B.N. Breizman PRL 114, 155001 (2015)



60

P-9: Measurement of the passive fast ion D-alpha emission on NSTX-U

G. Z. Hao1, W. W. Heidbrink

1, D. Liu

1, L.Stagner

1, M. Podesta

2, A. Bortolon

2, R.Bell

2,

D. S. Darrow2 and E. D. Fredrickson

2

1 University of California, Irvine, Irvine, CA 92697, USA

2 Princeton Plasma Physics Laboratory, Princeton, NJ 08543, USA

On NSTX-U, the passive fast-ion D-alpha (p-FIDA) spectra from the charge exchange between

the beam ions and the background neutrals are measured and simulated. In this study, the fast

ions mainly come from the axisymmetric confined population. The results indicate that, for the

passing fast ion population, the p-FIDA signal is comparable to the active FIDA (a-FIDA) on

several channels, such as at the major radius R=117cm. Here, a-FIDA means the D-alpha

emission from the fast ions that charge exchange with the injected neutrals. The measured

spectra have a good agreement with FIDASIM simulation on certain fibers. In addition, the p-

FIDA profile obtained from the integration in the energy component region (20~50 keV) agrees

with the simulation. In addition, for the trapped fast ion population, the p-FIDA is much smaller

than (<=15%) the a-FIDA. In conclusion, it is suggested that for measuring the passing fast ion

population, the p-FIDA signal is considerable, and the calculation of the p-FIDA should be

employed when reference-view background subtraction is not used. In addition, it is implied that

p-FIDA technique may be used to monitor the passing fast ions in the edge region on spherical

tokamak.

Work supported by U.S. DOE DE-AC0209CH11466, DE-FG02-06ER54867, and DE-FG03-

02ER54681

61

P-10: Nonlinear energetic particle transport by Alfvén eigenmodes and sensitivity study of

hybrid-gyrokinetic physics models

Thomas Hayward-Schneider, Philipp Lauber

Max-Planck-Institut für Plasmaphysik (IPP), 85748 Garching, DE


Alfvén eigenmodes, driven unstable by energetic particles, have the capability to transport

particles and energy in a fusion reactor via resonant wave-particle interaction. Whilst it is not

expected that the amplitudes of individual saturated Alfvén eigenmodes will be sufficiently

large to cause significant transport, it is possible that the interplay between different modes will

lead to increased transport. The scope of this work is to perform an investigation into the

thresholds of the transport, and perform a quantitative analysis into the transition to different

transport regimes.

The eigenvalues (mode frequency and damping) and eigenvectors (radial mode structure) from

the linear gyrokinetic code LIGKA have previously been used as input to the hybrid HAGIS

code. In order to create a tool capable of performing fast studies to investigate systematic

sensitivity to changes in the magnetic profiles and plasma parameters, the LIGKA model has

been built as a library, which is now invoked directly from HAGIS. Depending on the physics

required, the LIGKA model can perform local or global, MHD or kinetic mode calculation.

In this work, a sensitivity study is performed, showing how the physics model taken for the

eigenvalue calculation affects the transport. Results for many modes in ITER are presented,

noting that in contrast to current experiments, the number of unstable Alfvén eigenmodes in

ITER or DEMO is expected to be large.

Coupled HAGIS-LIGKA simulations for a series of Alfvén eigenmodes in the ITER standard

15MA scenario are presented, with sensitivity to plasma profiles investigated. Linear and

nonlinear results show the growth rates and saturation amplitudes of single mode simulations,

showing scalings between saturation amplitudes and linear physics. Additionally, nonlinear

multimode results show the effects of interacting modes on the saturation amplitudes.


62

P-11: Global Alfvén Eigenmodes in the H-1 heliac

M.J. Hole1, B. D. Blackwell

1, G. Bowden

1, M. Cole

2, A. Könies

2, C. Michael

1, F. Zhao

1 and

S. R. Haskey3

1Research School of Physics & Eng. Australian National University, ACT 0200, Australia

2 Max Planck Institute for Plasma Physics, D-17491 Greifswald, Germany

3 Princeton Plasma Physics Lab., P.O. Box 451, Princeton, New Jersey 08543-0451, USA

E-mail of Corresponding Authors: [email protected]

Recent upgrades in H-1 power supplies have enabled the operation of the H-1 experiment at

higher heating powers than previously attainable. A heating power scan in mixed

hydrogen/helium plasmas reveals a change in mode activity with increasing heating power. At

low power (<50 kW) modes with beta-induced Alfvén eigenmode (BAE) frequency scaling are

observed. At higher power modes consistent with an analysis of nonconventional global Alfvén

Eigenmodes (GAEs) are observed, the subject of this work.

We have computed the mode continuum, and identified GAE structures using the ideal MHD

solver CKA[1] and the gyrokinetic code EUTERPE[2]. An analytic model for ICRH-heated

minority ions is used to estimate the fast ion temperature from the hydrogen species. Linear

growth rate scans using a local flux surface stability calculation, LGRO [3], are performed.

These studies demonstrate growth from circulating particles whose speed is significantly less

than the Alfvén speed, and are resonant with the mode through harmonics of the Fourier

decomposition of the strongly-shaped heliac magnetic field. They reveal drive is possible with

a small (nf / n0 < 0.2) hot energetic tail of the hydrogen species, for which Tf > 300 eV. Local

linear growth rate scans are also complemented with global calculations from CKA and

EUTERPE. These qualitatively confirm the findings from the LGRO study, and show that the

inclusion of finite Larmor radius effects can reduce the growth rate by a factor of three, but do

not affect marginal stability.

Finally, a study of damping of the global mode with the thermal plasma is conducted,

computing continuum damping, and the damping arising from finite Larmor radius and parallel

electric fields (via resistivity). We find that continuum damping is of order 0.1% for the

configuration studied. A similar calculation in the cylindrical plasma model produces a

frequency 35% higher and a damping 30% of the three dimensional result: this confirms the

importance of strong magnetic shaping to the frequency and damping. The inclusion of

resistivity lifts the damping to / = -0.189. Such large damping is consistent with experimental

observations that in absence of drive the mode decays rapidly (~0.1 ms).

References:

[1] Axel Könies. A code for the calculation of kinetic Alfvén waves in three-dimensional Geometry. 10th

IAEA TM on Energetic Particles in Magnetic Confinement Systems, 2007.

[2] G. Jost, T. M. Tran, W. A. Cooper, L. Villard, and K. Appert. Global linear gyrokinetic simulations

in quasi-symmetric configurations. Phys. Plas., 8(7):3321–3333, 2001.

[3] A. Könies, A. Mishchenko, and R. Hatzky. From kinetic MHD in stellarators to a fully kinetic

description of wave particle interaction. In Theory of Fusion Plasmas, AIP Conference Proceedings,

volume 1069, page 133, 2008


63

P-12: ORBIT modelling for fast particle redistribution induced by sawtooth instability

D. Kim, M. Podestà and F. Poli

Princeton Plasma Physics Laboratory, Princeton, NJ 08543, USA


The sawtooth instability is a periodic fast collapse of the plasma parameters with a slower

recovery in the central region of a tokamak plasma, where the safety factor q is below unity.

After a sawtooth crash, the q profile is flattened and q0 ≥ 1 (complete reconnection [1]) or q0

remains below one (incomplete reconnection [2]) and plasma particles are redistributed

depending on the reconnection type. Fast ions, e.g. from Neutral Beam injection, are also

redistributed by sawteeth. Unlike thermal plasma, the redistribution depends on fast ion energy

[3]. Initial tests on NSTX-U show that introducing energy selectivity for sawtooth induced fast

ion redistribution improves the agreement between experimental and simulated (via TRANSP

[4]) quantities such as neutron rate. Therefore, it is anticipated that an appropriate description of

the fast particle redistribution produced by sawtooth crashes can improve the modelling of

sawtooth instabilities and its application to a transport code such as TRANSP can improve

interpretation of experiments. In this work, we use the particle-following ORBIT code [5] to

characterise the redistribution of fast particles. In order for a sawtooth crash to be simulated, a

spatial and temporal displacement is implemented into ORBIT code as 𝜉(𝜌, 𝑡, 𝜃, 𝜑) = ∑ 𝜉𝑚𝑛( 𝜌, 𝑡)cos (𝑚𝜃 + 𝑛𝜑) [6, 7], where m, n, θ, φ are the poloidal and toroidal mode numbers

and angles, respectively. The displacement can produce perturbed magnetic fields from the

equilibrium field �� , 𝛿�� = ∇ × (𝜉 × �� ), which affect the distribution of fast particles. From

ORBIT simulations, we find suitable amplitudes of ξ with different mode numbers (m, n) for

each sawtooth crash case to reproduce the experimental results. The comparison of the

simulation and the experimental results, e.g. neutron rate, will be discussed as well as the

characterised energy, pitch angle and magnetic moment dependence of fast ion redistribution.

References:

[1] Kadomtsev B. 1976 Sov. J. Plasma Phys. 1 710

[2] Porcelli F., Boucher D. and Rosenbluth M.N. 1996 Plasma Phys. Controlled Fusion 38 2163

[3] Kolesnichenko Ya. I., Lutsenko V.V. and Yakovenko Yu. V. 1997 Phys. Plasmas 4 2544

[4] Hawryluk R. 1979 An empirical approach to tokamak transport Proc. of Physics of Plasmas Close to

Thermonuclear Conditions, volume 1 (International School of Plasma Physics, Varenna, Italy, 27

August–8 September 1979)

[5] White R.B. and Chance M.S. 1984 Phys. Fluids 27 2455 [6] Igochine V. et al 2007 Nucl. Fusion 47 23

[7] Farengo R. et al 2013 Nucl. Fusion 53 043012

Work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy

Sciences under contract number DE-AC02-09CH11466.


64

P-13: Suppressing Alfven eigenmodes in high-performance discharges

G.J. Kramer1, C. Holcomb

2, W.W. Heidbrink

3, C. Collins

2, R. Nazikian

1, M.A. Van Zeeland

4

and Y. Zhu3

1

Princeton Plasma Physics Laboratory, PO Box 451, Princeton, NJ 08543, USA 2

Lawrence Livermore National Laboratory, Livermore, CA 94550, USA 3

University of California Irvine, Irvine, CA 92697, USA 4

General Atomics, San Diego, CA 92186, USA

E-mails of Corresponding Authors: [email protected], [email protected],

[email protected], [email protected], [email protected], [email protected],

[email protected]

Enhanced fast-ion transport can be problematic in DIII-D for reaching a steady-state regime in

high low-shear discharges because it reduces the neutral-beam current drive and limits the

that can be obtained, making it difficult to drive a sufficient bootstrap current to reach steady

state [1].

Fast-ion transport in DIII-D in steady-state scenarios was found to be driven by Alfven

eigenmodes [2]. The most harmful modes are the Reversed Shear Alfven eigenmodes (RSAE)

that are located near qmin at r/a=0.3 and coincide with the maximum fast-ion pressure gradient

that drive those modes [3]. Moving qmin outward and away from the maximum drive can reduce

the RSAE activity to benign levels as was shown for a steady-state discharge with a reduced

plasma current (0.6 MA).

Based on these results, experiments were performed to create 1 MA discharges with a larger qmin

radius to suppress the RSAE activity in a similar way. A modest increase in the qmin radius was

obtained by a very fast current ramp rate (7 MA/s) and very early beam injection (70 ms after

break-down) and the AE activity was suppressed from 0.3~s to well after 1~s. However, qmin

was formed around r/a= 0.4 and drifted inward during this interval so the suppression of RSAEs

in this case cannot be accounted for by a reduction in the fast-ion drive because qmin is still

located in the strong fast-ion pressure gradient region. We show in this presentation that RSAEs

can be suppressed by reducing the low-shear region near qmin thereby limiting the AE-induced

fast-ion transport.

References:

[1] C.T.~Holcomb et al. Phys. Plasmas 22 055904 (2015)

[2] W.W.~Heidbrink et al. Plasma Phys. Control. Fusion 56 095030 (2014)

[3] G.J.~Kramer el al. Nucl. Fusion 57 058024 (2017)

Work supported by DOE contracts DE-AC02-09CH11466, DE-AC52-07NA27344, DE-FC02-

04ER54698, and SC-G903402.








65

P-14: The Effect of Ferritic Inserts on Fast Ions in DEMO

T. Kurki-Suonio1, J. Varje

1, A. Snicker

1 and P. Vincenzi

2

1Aalto University, Otakaari 1, 02015 Espoo Finland

2Consorzio RFX, Corso Stati Uniti 4 - 35127 Padova (Italy)

Due to the need of demonstrating tritium breeding, the tolerance for power loads will be quite

low for the first-wall components in DEMO. Therefore every precaution should be taken to

reduce the power arriving at the wall. In the case of fusion alphas and other fast ions, this means

striving towards approximate axisymmetry, which can be achieved with ferritic inserts (FI).

The first ASCOT simulations on the effects that ferritic inserts can have on fast ions revealed

that the quality of the default magnetic backgrounds, purely calculated utilizing FEM method,

was not sufficient but the numerical drift caused severe anomalies in the slowing-down

distributions.

In this work, a cost-efficient way of obtaining high-resolution, high-quality fields was used:

First, a FEM-solver (here: commercial COMSOL package) is used to calculate the magnetizing

field from the geometry and currents in the coils and plasma. In the second step, the magnetized

components (in this case the ferritic inserts) are modelled as permanent magnets, and COMSOL

calculates the field they produce. In the final step, this perturbation field is added to the global

vacuum field calculated at high-resolution using a Biot-Savart solver.

Using the 2015 DEMO1 pulsed flattop scenario [1] plasma density and temperature profiles and

equilibrium, both fusion alphas and beam ions were simulated for the unmitigated TF ripple

case and the ferritic insert cases with 25%, 50%, 75% and 100% FI mass to assess the

effectiveness of ripple mitigation. For the beams, the latest DEMO reference design [1] was

used, consisting of 3 injectors of 16.8MW each, with 800 keV particle energy. Each injector is

made of 20 independent negative ion sources aligned in two vertical columns, with 60 beamlets

in each source.

For fusion alphas, the total losses were less than 0.5 MW even for the unmitigated ripple. The

ferritic inserts provide an order of magnitude reduction in the losses already at 50% of the

design mass, indicating excellent ripple mitigation performance. To accurately assess the peak

wall loads, the wall tiles were subdivided into smaller triangles for increased spatial resolution,

and the losses were remapped to a single 20-degree sector to take advantage of the 18-fold

symmetry of the wall and the toroidal magnetic field. The largest power load is concentrated on

the outer midplane, with the peak loads remaining below 50 kW/m2. The confinement of the

NBI ions was found to be good (lost power ~ 50 kW) even in the unmitigated ripple case, and

with the ferritic inserts the losses were further reduced by more than 90%.

In addition, no differences were observed in the slowing-down densities due to the 3D effects

introduced by the ferritic inserts. The total NBI driven torque for a single 16.8 MW beam was

25.2 Nm.

References:

[1] R. Wenninger et al., Nuclear Fusion 57 (2017) 016011

[2] P. Sonato et.al., Nuclear Fusion 57 (2017) 056026

66

Fig. 1. Change in frequency for |n|=8 GAEs as

a function of the normalized injection velocity

𝒗𝒃/𝒗𝑨. Cntr-GAEs are marked by circles, co-

GAEs by squares. Color denotes the central

pitch 𝝀𝟎 = 𝝁𝑩𝟎/𝜺 of the beam distribution in

each simulation. The on-axis cyclotron

frequency is 2.4 MHz.

P-15: Energetic-particle-modified global Alfvén eigenmodes

J.B. Lestz1,2

, E.V. Belova2, N.N. Gorelenkov

2

1Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08543, USA

2Princeton Plasma Physics Laboratory, Princeton, NJ 08543, USA

E-mails of Corresponding Authors: [email protected], [email protected], [email protected]

Fully self-consistent hybrid MHD/particle

simulations reveal strong energetic particle

modifications to sub-cyclotron global Alfvén

eigenmodes (GAE) in low-aspect ratio, NSTX-like

conditions. Key parameters defining the fast ion

distribution function – the normalized injection

velocity 𝑣𝑏/𝑣𝐴 and central pitch – are varied in

order to study their influence on the characteristics

of the excited modes. It is found that the frequency

of the most unstable mode for each toroidal

harmonic changes significantly and continuously

with beam parameters, depending most

substantially on 𝑣𝑏/𝑣𝐴 , as shown in Fig. 1. This

unexpected result is present for both co- and

counter-propagating GAEs, where the linear

dependence and sign of the change are consistent

with the Doppler-shifted cyclotron resonances

which drive the modes. However, there are no

clear concurrent changes in mode structure (i.e.

poloidal or radial mode numbers) that would indicate that these frequencies correspond to

distinct eigenmodes, especially for the co-GAEs. Additional simulations conducted for a fixed

MHD equilibrium demonstrate that the GAE frequency change cannot be explained by the

equilibrium changes due to energetic particle effects.

An energetic particle mode (EPM) defined by a continuum of 𝑘∥ values to choose from as the

injection velocity is varied is consistent with these findings, and could indicate the existence of a

new EPM, referred to here as an energetic-particle-modified GAE (EP-GAE). This may be the

first instance of an EPM driven by the cyclotron resonance and excited at an appreciable fraction

of the cyclotron frequency instead of near EP orbital frequencies. The simulations presented

here show that the nonperturbative regime for these modes was routinely accessed in NSTX

operating conditions. The basic picture of an energetic beam driving an MHD mode of the

thermal plasma without modifying its attributes is seen to break down in conditions where 𝐽𝑏𝑒𝑎𝑚

is comparable to 𝐽𝑝𝑙𝑎𝑠𝑚𝑎 . This may have implications for the ongoing investigation into the

anomalously flat 𝑇𝑒 observed in NSTX at high beam power, which is correlated with substantial

high frequency Alfvenic activity [1]. Prospects for future experimental verification of the EP-

GAE are promising, as its defining characteristics should be observable in suitably designed

experiments on NSTX-U.

References:

[1] D. Stutman, L. Delgado-Aparicio, N. Gorelenkov, et al. Phys Rev Lett 102, 115002 (2009)




67

P-16: Effect of Sawtooth crashes on fast-ion distribution in NSTX-U

D. Liu1, W. W. Heidbrink

1, G. Z. Hao

1, M. Podesta

2, E. D. Fredrickson

2 and D. S. Darrow

2

N. A. Crocker3, S. Kubota

3 and W. W. Heidbrink

1

1University of California, Irvine, USA

2Princeton Plasma Physics Laboratory, USA

3University of California, Los Angeles, CA 90095, USA


During the 2016 experimental campaign of NSTX-Upgrade (NSTX-U), long L-mode and

reproducible sawtoothing plasmas have been achieved that were previously not accessible on

NSTX. This provides a good opportunity to investigate the conditions of sawtooth appearance

and to study their effects on fast ion confinement and re-distribution in spherical tokamaks. The

Fast-Ion D-alpha (FIDA) and Solid State Neutral Particle Analyzer (SSNPA) diagnostics on

NSTX-U each has two subsystems with one subsystem more sensitive to passing particles and

the other one more sensitive to trapped particles. It has been observed on both diagnostics that

the passing particles are strongly expelled from the plasma core to the plasma edge during

sawtooth crashes while trapped fast ions are weakly affected. The tangential-FIDA (t-FIDA)

system which is most sensitive to passing particles saw a signal drop in the region inside the

inversion radius (~125cm), while an increase at the outer region. The neutron rate can drop as

much as 13% during sawtooth crashes. This phenomenon is similar to previous observations in

DIII-D and ASDEX Upgrade conventional tokamaks. Detailed data analysis and modelling are

being performed to quantity the effects of sawtooth crashes on fast-ion redistribution and to

compare with the Kadomtsev sawtooth model.


68

P-17: Detection and investigation of Alfven Eigenmodes with Heavy Ion Beam Probe in the

TJ-II stellarator

A.V. Melnikov1, 2

, E. Ascasibar3, A. Cappa

3, F. Castejon

3, L.G. Eliseev

1, C. Hidalgo

3,

P.O. Khabanov1, N.K. Kharchev

1, A.S. Kozachek

4, L.I. Krupnik

4, M. Liniers

3, S.E.Lysenko

1,

J.L. dePablos3, V.N. Zenin

1, A.I. Zhezhera

4, and TJ-II team

2

1 National Research Centre “Kurchatov Institute”, 123182, Moscow, Russia

2 National Research Nuclear University “MEPhI”, Moscow, Russia

3 Fusion National Laboratory, CIEMAT, 28040, Madrid, Spain

4 Institute of Plasma Physics, NSC KIPT, 310108, Kharkov, Ukraine

Alfven Eigenmodes were studied in low magnetic shear flexible heliac TJ-II (B0=0.95 T,

<R>=1.5 m, <a>=0.22 m) NBI heated plasmas (PNBI1.1 MW, ENBI=32 keV) by Heavy Ion

Beam Probe (HIBP) [1, 2, 3]. The L-mode hydrogen plasma was investigated at various

magnetic configurations with rotational transform a/2q ~ 1.5 - 1.6. Co-, counter and

balanced beam injection were explored. HIBP is capable to measure simultaneously the

oscillations of the plasma electric potential, density and poloidal magnetic field. Earlier studies

have shown the chirping modes with 250 kHz< fAE <380 kHz at the low density ne = (0.3 –

1.5)×1019

m-3

NBI heated plasmas with or without auxiliary ECR [3, 4]. Here we report the

observation of the various types of the chirping modes, differs by frequency, radial location,

amplitude and shape of the frequency dependence on time. Remarkably, the same mode may

evolve, changing its type in the same frequency range in the single discharge. HIBP shows that

location of the specific AE chirping may vary from = 0 up to = 0.8. The mode amplitude in

potential varies from a few Volts up to 100 V. AEs are strongly affected by plasma current Ipl,

e.g. caused by Ohmic heating coils. A variation of Ipl may even suppress the modes. Dual HIBP

[5], consisting of the two HIBPs, separated at ¼ of the torus shows the high coherence between

the plasma potential and density oscillations during the period of the frequency burst. The radial

scan of the HIBP sample volume indicates the radial evolution of the potential and density

perturbation during a single frequency burst of the chirping mode. Mean frequency of the

chirping modes basically follow the model, based on the Alfven scaling and including actual

iota evolution caused by Ipl changes [6].

References:

[1] R. Jiménez-Gómez et al Nuclear Fusion 51 (2011) 033001

[2] A.V. Melnikov et al Nuclear Fusion 50 (2010) 084023

[3] K. Nagaoka et al Nuclear Fusion 53 (2013) 072004

[4] A.V. Melnikov et al Nuclear Fusion 56 (2016) 076001

[5] J.L. De Pablos et al SOFT 2014, P1.060.

[6] A. Melnikov et al, Nuclear Fusion 54 (2014) 123002

69

P-18: Quantitative evaluation of the wall heat load by lost fast ions in the Large Helical

Device

J. Morimoto1, R. Seki

1,2, Y. Suzuki

1,2

1SOKENDAI (The Graduate University for Advanced Studies), Gifu, Japan

2National Institute for Fusion Science, Gifu, Japan.


To design fusion reactors, the localized heat load by lost fast ions, which cause damages on a

device and limit operational conditions, is a critical issue. In particular, a larger number of fast

ions in stellarator is lost than in tokamak. The prediction of the heat load by lost fast ions is

important in order to design stellarator fusion reactors.

The reactor relevant high beta plasma with volume averaged beta <>~5％ was achieved in the

Large Helical Device (LHD) [1]. The equilibrium magnetic field in high beta plasma is different

from the vacuum magnetic field in certain respects. These include the width of stochastic region

and the position of magnetic axis. On the other hand, the conventional analyses of the heat load

distribution on the divertor plates in stellarator [2] are investigated by using the field line tracing

in the vacuum magnetic field. Further, the effect of fast ions has not been included. To predict

the heat load distribution in the future fusion reactor, it is necessary to clarify the beta value

dependence of the heat load distribution by lost fast ions and to validate the simulation through

the systematic comparison with experimental observations.

To investigate the finite beta effect on the heat load by lost fast ions in LHD, a 3D Monte-Carlo

code called the GCR code [3] which follows guiding center orbits in real coordinate is

improved. The 3D equilibrium configuration of the LHD in real coordinate is computed with

HINT [4], a 3D free boundary MHD equilibrium code. In this study, hydrogen fast ions

produced by neutral beam injection (NBI) are traced until they are thermalized or strike the

vacuum vessel. The heat load distribution by lost fast ions is evaluated using the strike points of

fast ions and their energy.

In the case of the vacuum magnetic field, the heat load of fast ions produced by NBI

concentrated on the divertor plates from the inside to the upper region of the torus. In the case of

finite beta equilibrium field, the heat load is concentrated on the divertor plates from the inside

to the lower region of the torus. Although the strike points of fast ions deviate from the

footprints of magnetic field lines, this tendency is similar to the magnetic field lines.

The quantitative evaluation of the heat load on the plasma-facing component and the

comparison of simulation results with experimental data obtained by the Langmuir probes

embedded on the divertor plates in LHD will be reported at the meeting in detail.

References:

[1] S. Sakakibara, Plasma Phys. Control. Fusion, 50, 124014 (2008).

[2] S. Masuzaki et al., Nucl. Fusion, 42, 750 (2002).

[3] Y. Suzuki, Nucl. Fusion, 46, 123 (2006).

[4] Y. Suzuki et al., Nucl. Fusion, 46, L19 (2006).


70

P-19: TAE stability calculations compared to TAE antenna results in JE

F. Nabais1, V. Aslanyan

2, D. Borba

1, R. Coelho

1, R. Dumont

3, J. Ferreira

1, A. Figueiredo

1,

M. Fitzgerald4, J. Mailloux

4, P. Rodrigues

1, P. Puglia

5, S. E. Sharapov

4 and JET Contributors

*

EUROfusion Consortium, JET, Culham Science Centre, Abingdon, OX14 3DB, UK 1Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, 1049-001

Lisboa, Portugal. 2

MIT PSFC, 175 Albany Street, Cambridge, MA 02139, US 3CEA, IRFM, F-13108 Saint Paul Lez Durance, France

4CCFE, Culham Science Centre, Abingdon OX14 3DB, UK

5Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Plasma Center (SPC), CH-1015

Lausanne, Switzerland

The excitation of modes in TAE gap by an external antenna can be modelled by a driven damped

harmonic oscillator. A frequency scan makes possible to determine the damping rate through the

quality factor. This method has been employed in recent JET M 15-24 experiments (scenario

development for the observation of alpha-driven instabilities in JET DT plasmas) [1] and

damping measurements for two different pulses have been obtained. It is then of great

importance to compare the experimental measurements with the results from calculations

performed by numerical codes.

This paper describes the modelling method and presents the numerical simulations carried out

with using a suite of codes to calculate the damping, which are compared with experimentally

measured values. The modes under consideration are not observed experimentally since the

damping overcomes the drive provided by an ICRH accelerated population, so several modes

with frequencies close to the experimental value are calculated with the ideal MHD code

MISHKA [2]. For each of these modes, the damping on thermal ions, thermal electrons and the

drive provided by the ICRH accelerated ion population is calculated with the CASTOR-K code

[3]. Radiative damping is estimated using a complex resistivity in the CASTOR code [4], as

described in ref. [5]. The continuum damping is also estimated using also the CASTOR code.

Taking into account the calculated drive and all the considered forms of damping, the global

damping rates agree reasonably well with the experimental measurements for the selected

modes. Possible sources of uncertainties are discussed.

References:

[1] J. Mailloux et al. “Plasma preparation for alpha-particle excitation of TAEs in JET DT plasmas“,

presented at 44th EPS Conference, June 2017, Belfast, North Ireland

[2] A.B. Mikhailovskii et al. 1997 Plasma Phys. Rep. 23 844

[3] D. Borba et al. 1999 J. Comput. Phys. 153 101

[4] W. Kerner et al. 1998 J. Comput. Phys. 142 271

[5] A. Figueiredo et al. Nucl. Fusion 56 (2016) 076007



agreement No 633053. IST activities also received financial support from “Fundação para a

Ciência e Tecnologia” through project UID/FIS/50010/2013. The views and opinions expressed

herein do not necessarily reflect those of the European Commission.

* See the author list of “X. Litaudon et al 2017 Nucl. Fusion, 57, 102001”

71

P-20: Nonlinear interaction of fast ions with Alfvén eigenmodes - Control and

measurement of distribution function of fast ions

K. Nagaoka ab, A. Azegamib, M. Osakabe ac, M. Isobe ac, K. Ogawa ac, Y. Suzuki ac, R. Seki a,

S. Kamio a, M. Shibuya, H. Yamaguchi a, S. Kobayashi d, S. Yamamoto d, K. Nagasaki d,

A. Cappae, J.M. Fontdecaba

e, and E. Ascasibar

e

a National Institute for Fusion Science, Natural Institutes of Natural Sciences, Toki 509-5292,

Japan bGraduate School of Science, Nagoya University, Nagoya 464-8602, Japan

cSOKENDAI (The Graduate Univerisity for Advanced Studies), Toki 502-5092, Japan

d Institute of Advanced Energy, Kyoto University, Uji, 611-0011, Japan

e Ciemat, Av. Computense, Madrid, Spain


Stability and nonlinear phenomena of energetic-particle-driven Alfvén eigenmodes are

fundamental and challenging subjects of plasma physics, and kinetic consideration is required.

In the experimental study, control and measurement of distribution function of fast ions are key

for understanding the behaviors of Alfvén eigenmodes. In this paper, two experimental studies

are discussed: one is control of fast-ion profile and the other is measurement of response of

velocity distribution function of fast ions interacting with Alfvén eigenmodes.

<Control> In the Large Helical Device (LHD), the experimental study of Alfvén eigenmodes

was carried out with peaked, flat and hollow profiles of fast ions, which were produced by the

combination of ion source (IS) operation of tangential NBIs and the magnetic configuration of

the plasma. It was observed that excitation of some Alfvén eigenmodes strongly depend on the

fast ions profiles.

<Measurement> In order to evaluate responses of fast ion velocity distribution function

interacting with Alfven eigenmodes, the wave-particle interaction analyzer (WPIA) was

developed and applied for plasma experiments in LHD, Heliotron J and TJ-II. The preliminary

results will be discussed in the conference.

These experimental approaches are new challenges to understand the nonlinear phenomena

caused by kinetic effects of fast ions and the related discussions in the conference seem to be

fruitful, while the results are still preliminary.


72

P-21: Experimental evaluation of nonlinear collision effect on the beam slowing-down

process

H. Nuga1, R. Seki

1,2, S. Kamio

1, M. Osakabe

1,2, M. Yokoyama

1,2, M. Isobe

1,2, K. Ogawa

1,2, and

LHD experiment group

1National Institutes for Natural Sciences, National Institute for Fusion Science, Toki, Japan

2SOKENDAI (The Graduate University for Advanced Studies), Toki, Japan


Achieving high performance of energetic particle confinement is one of the most important

issues for fusion reactors. Although the self-sustained plasma by fusion-born fast α particles is

necessary to realize fusion power plant, the confinement performance of the fusion plasma is

often degraded by the fast particle driven phenomena. Because of this reason, the behavior of

energetic particles has been investigated in several devices and simulations. In our group,

Fokker-Planck code, TASK/FP[1], has been implemented as a Fokker-Planck component of the

integrated simulation code TASK3D-a[2] to analyze the behavior of fast particles. In the present

paper, in order to validate our Fokker-Planck code, Fokker-Planck analyses and experimental

evaluations of the nonlinear collision effect to the beam slowing down process in deuterium

plasmas are investigated. Contrary to the linear collision model, which assumes the background

velocity distribution to be Maxwellian, the nonlinear collision model can include the

contribution of beam-beam collision effect to the beam slowing down process. The nonlinearity

can be demonstrated experimentally through the observation of the evolution of neutron

emission rate from D-D fusion reaction as follows. Three tangential neutral beam injection

systems are equipped on LHD. Two of them, NB#1 and NB#2, are hydrogen ion beam in

different direction. Rest of them, NB#3, is deuterium ion beam same direction to NB#1. They

have nearly same beam energy E ∼ 140 − 180 keV. Since the beam-thermal DD reaction is

dominant within the LHD plasma parameters, the neutron emission rate decays after NB#3 offs.

If hydrogen beam same direction to deuterium beam (NB#1) is injected into the plasma as

background NB, the decay time of the neutron emission rate may become longer due to beam-

beam collision because the H beam is faster than the D beam. Fig. 1 shows the preliminary

simulation result of the decay time of neutron emission rate. The decay time is plotted with

respect to the beam slowing down time. Fig. 2 shows experimental results. Qualitatively same

tendency appears between simulations and experiments.

Fig.1. Fig.2.


73

P-22: Energetic Particles within ITER’s Integrated Modelling & Analysis Suite

S.D. Pinches1, R.J. Akers

2, G.T.A Huijsmans

3, T. Jonsson

4, Ph. Lauber

5, M. Salewski

6,

M. Schneider1, S.E. Sharapov

2, S. Ward

7, ITPA Energetic Particle Physics Topical Group

and IMAS Contributors

1 ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St Paul Lez Durance

Cedex, France 2Culham Centre for Fusion Energy, Culham Science Centre, Abingdon, Oxon, OX14 3DB, UK

3CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France

4Royal Institute of Technology, VR-Euratom Association, Teknikringen 31, 100 44 Stockholm,

Sweden 5Max-Planck-Institute for Plasma Physics, Boltzmannstr. 2, D-85748 Garching, Germany

6Technical University of Denmark, Department of Physics, Fysikvej, DK-2800 Kgs. Lyngby,

Denmark 7Department of Physics, University of York, Heslington, York, YO10 5DD, UK


The ITER Integrated Modelling Programme supports the refinement and execution of the ITER

Research Plan through a modelling framework and set of software tools capable of describing,

inter alia, ITER scenarios including representations of actuators, diagnostics and control

capabilities (delivered through coupling with the Plasma Control System Simulation Platform).

A consequence of the ITER Project Requirements being placed on measurements rather than

specific diagnostics is the encouragement of an integrated approach to combining measurements

from separate systems to deliver a single measurement parameter or profile with its associated

uncertainties. Such an approach to reconstruct the confined fast ion distribution is presently the

focus of an ITPA joint activity being conducted within the Energetic Particle Physics Topical

Group across a range of the ITER Members’ devices.

An accurate knowledge of the expected ITER plasma scenarios and fast ion distribution

functions contained therein is necessary to be able to make stability assessments and to examine

the expected losses of fast ions to the first wall and divertor. As a first step, a benchmarking

exercise has been initiated, again under the auspices of the ITPA Topical Group on Energetic

Particle Physics, to compare the present state of the art tools for describing the auxiliary heating

systems foreseen to generate fast ions in ITER, namely neutral beam injection and ion cyclotron

heating.

In parallel with this benchmarking exercise, a comprehensive integrated modelling workflow

specifically targeted at describing heating and current drive (including synergistic effects) has

been developed for use within workflows simulating plasma evolution. The use of the standard

ITER Data Model capable of representing both experimental and simulation data will facilitate

the validation of such predicted fast ion distributions by allowing comparison with the

integrated diagnostic reconstruction of the fast ion distribution on existing devices as outlined

above.

In this paper, the status of the implementation of various energetic particle workflows in IMAS

is described together with ongoing work on the demonstration of a first machine-independent

plasma reconstruction chain. The aim here is that the use of this reconstruction chain rather than

just being a simple validation in preparation for ITER, will also add value to present

experimental programmes by allowing more direct comparisons between machines thereby

helping to underpin the extrapolation of results to ITER.


74

P-23: Hard X-ray Bremsstrahlung of Relativistic Runaway Electrons in JET

V.V. Plyusnin1, V.G. Kiptily

2, A.E. Shevelev

3, E.M. Khilkevitch

3 and JET contributors

*

EUROfusion Consortium, JET, Culham Science Centre, Abingdon, OX14 3DB, UK 1Instituto de Plasmas e Fusão Nuclear, Instituto Superior Tecnico, Universidade de Lisboa,

Lisboa, Portugal 2CCFE, Culham Science Centre, Abingdon, OX14 3DB, UK

3Ioffe Institute, St. Petersburg, 194021, Russia


One of the main requirements to disruption mitigation system in ITER (ITER DMS) is the

capability to avoid/suppress detrimental runaway electron (RE) generation. A detailed

understanding of the physics of runaways and their evolution during disruptions is one of the

key conditions to achieve necessary capabilities of ITER-DMS on RE avoidance/suppression.

Relativistic RE interacting with background plasma ions and neutrals produce the

bremsstrahlung in energy range till to MeV energies that corresponds to the emission of hard X-

rays (HXR) and -rays. Hitting the plasma-facing components (PFCs) RE produce photo-

neutrons also. Measurement of HXR/’s and photo-neutrons provide detailed information on RE

generation. In this article we present the combined analysis of HXR/ images and subsequent

numerical assessment of parameters of RE beams generated in JET.

The spatial distribution of HXR sources in JET plasmas has been measured with the JET

neutron/-ray profile monitor routinely used for neutron and -ray measurements. The monitor

consists of two cameras, vertical and horizontal, with 9 and 10 highly collimated lines of sight

(LoS), respectively. The HXR spectra have been measured with the sets of horizontally and

vertically viewing NaI(Tl), Bi4GeO12 (usually referred as BGO) and LaBr3 spectrometers. The

raw data from spectrometers has been processed numerically to get the energy spectra of RE.

Inferred RE energy values have been compared to those obtained in numerical simulations. This

comparison and several recent results highlight an apparent difference between RE energy

deduced from the HXR measurements and from the modeling. Analysis of HXR bremsstrahlung

has been carried out to resolve this problem.

The angular distribution of the HXR radiation from relativistic RE scattered off by plasma

ions/neutrals has a strong anisotropy in the direction of the electron velocity with half-width of

the radiation pattern: 𝜃~1𝛾0

⁄ (𝛾0 = 𝐸/𝑚𝑐2- Lorentz parameter). This radiation pattern will

have limited move up and down because of the RE helical motion on the toroidal surface. The

geometry of HXR radiation transmission lines and extremely high collimation of

HXR/detectors rule out the observation of HXR emission with the forward radiation pattern:

𝜃~1𝛾0

⁄ at large angles ( ~ 𝜋/2 ). However, the JET HXR diagnostics have detected the

significant HXR bremsstrahlung emission with obvious asymmetry of HXR sources.

Measurements in poloidal plane revealed many HXR emission spots in the JET plasma core

during disruptions with surprisingly narrow radiation patterns (𝜃~1𝛾0

⁄ ) corresponding to the

energies close to those inferred from the HXR spectra. Analysis of the bremsstrahlung

* See the author list of “Litaudon et al, Overview of the JET results in support to ITER, accepted for publication in

Nuclear Fusion”


75

parameters and mapping of HXR sources have shown that possibility to measure HXR emission

in perpendicular direction appears when the Compton scattering of the bremsstrahlung is

considered in analysis. Accomplished study has shown necessity to take into account the

Compton scattering in the analysis HXR bremsstrahlung parameters and RE generation

dynamics including evaluation of RE energies.

“This work has been carried out within the framework of the EUROfusion Consortium and has


agreement No 633053. The views and opinions expressed herein do not necessarily reflect those

of the European Commission.”

76

P-24: Analysis of the nonlinear interaction of fast ion driven plasma waves

P. Zs. Poloskei1, G. Papp

2, G. I. Pokol

1, Ph. W. Lauber

2, X. Wang

2, L. Horvath

3

and the ASDEX Upgrade team2

1Institute of Nuclear Techniques, Budapest University of Technology and Economics, Hungary

2Max-Planck Institute for Plasma Physics, Garching, Germany

3York Plasma Institute, Department of Physics, University of York, York, UK


Adequate control of the transport of suprathermal ions is of crucial importance in fusion plasma

physics. Suprathermal ions are required to provide significant fraction of the plasma heating,

which is essential for self-sustaining fusion reactions. Furthermore, uncontrolled losses can

cause damage on plasma facing components. Fast ions can drive transient, global plasma waves,

which in turn lead to enhanced transport. Direct nonlinear wave-wave coupling can stabilize or

destabilize marginally stable energetic particle driven modes, heavily influencing particle and

energy losses. Therefore, understanding of direct wave-wave interactions is an open question of

interest for future fusion devices.

Bicoherence calculation is routinely applied to investigate second order nonlinearities of

stationary processes. Transients - which often appears in real measurements – can lead to high

bicoherence even in the lack of real phase coupling (false positives or Type I. errors). We have

generalized bicoherence calculation to transient phenomena, to eliminate these false positives

[1]. The method has been validated using simple nonlinear test systems.

The newly developed method was applied to hybrid MHD-gyrokinetic simulations with the

XHMGC [2] code. We have shown that indirect interaction of modes via only the fast particle

phase space –in the absence of explicit wave-wave coupling– does not lead to nonlinear

coupling, in accordance with theory. Extension of the study to wave-wave coupled cases is

planned in the near future.

We have performed dedicated experiments on the ASDEX Upgrade tokamak, where the

possible nonlinear interaction of fast ion driven EGAMs [3] and bursting TAEs [4] was

investigated. For the first time, we have found experimental evidence of significant quadratic

phase coupling between these modes, indicating direct wave-wave coupling interaction.

References:

[1] P. Zs. Poloskei, MSc thesis, Budapest University of Technology and Economics (2017)

[2] S. Briguglio et al., Physics of Plasmas, 2 3711 (1995)

[3] L. Horváth et al., Nuclear Fusion, 56 112003 (2016)

[4] M. Schneller et al., Plasma Phys. Control. Fusion 58 014019 (2015)


77

P-25: Fast-Ion Edge Resonant Transport Layer Induced by Externally Applied 3D Fields

in the ASDEX Upgrade Tokamak

L. Sanchis1, M. Garcia-Munoz

1, A. Snicker

2, J. Galdon-Quiroga

1, D. A. Ryan

4, M. Nocente

5,

J. F. Rivero-Rodriguez1, L. Chen

6, W. Suttrop

3, E. Viezzer

1, M. A. Van Zeeland

7,

ASDEX Upgrade and EUROfusion MST1 Teams*

1Dept. of Atomic, Molecular and Nuclear Physics, Universidad de Sevilla, 41012, Spain

2Dept. of Applied Physics, Aalto University, FI- 00076, Aalto, Finland

3Max Planck Institut für Plasmaphysik, Boltzmannstrasse 2, 85748, Garching, Germany;

4CCFE, Culham Science Centre, OX14 3DB, Abingdon, UK

5Universita degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy

6IFTS, Zhejiang University, 310027, 310027, Hangzhou, China

7General Atomics, CA 92186-5608, San Diego, USA


Recent experiments in the ASDEX Upgrade tokamak have revealed the existence of an Edge

Resonant Transport layer (ERTL) responsible for the fast-ion losses observed in the presence of

externally applied 3D fields [1]. The amplitude and velocity-space of the measured fast-ion

losses depends on the 3D field poloidal spectrum, the magnetic background helicity (q95) and

the plasma collisionality. Full orbit simulations carried out with the ASCOT code using the

plasma response calculated with MARS-F reproduce a strong correlation of fast-ion losses with

the 3D fields’ poloidal spectra showing also that toroidal sideband harmonics can modify

significantly the overall fast-ion losses, see Fig.1. An edge peeling amplification leads to 20%

enhancement of the total losses for a certain poloidal spectrum range while an internal kink

amplification leads to a local enhancement of the losses but not to a significant contribution to

the total losses. This work presents an analysis of fast-ion confinement in terms of the variation

of the toroidal canonical momentum (δPφ), which reveals resonant structures at the plasma edge

activated by 3D fields that match rational orbital resonances, see Fig.2. The concentration of

non-linear resonances at the edge plays a key role in the observed transport. The fast-ion

resonances depend strongly on the particle pitch angle, but not significantly on the particle

* H. Meyer et al. Nuclear Fusion FEC 2016 Special issue (2017)

Fig 1a. Total fast-ion losses modulated by Δϕ for

plasma response and vacuum approach. Fig 1b.

FILD signal and ASCOT simulated FILD signal

including plasma response as a function of Δϕ.

Fig 2. δPφ structures in the presence of a Δϕ=40º

MP configuration overlapped with matching

orbital resonances(ωpol/ωtor) using test particle

pitch =-0.5. Black-blue areas represent outwards

transport while yellow-white means inwards

transport.


78

energy suggesting that similar rational resonances may also exist for thermal ions. The δPφ

figure of merit presented here seems to be a powerful tool to predict the fast-ion confinement in

the presence of externally applied 3D fields with different configurations. The implications of

the results presented here for the fast-ion confinement in ITER with externally applied 3D fields

will be discussed through realistic full orbit simulations including plasma response.

References:

[1] M. Garcia-Munoz et al. IAEA FEC 2016 Kyoto, Japan

79

P-26: Demonstration of Loss Cone Induced Quasi-Longitudinal (QL) Whistlers in Large

Laboratory Plasma of LVPD

A. K. Sanyasi1,3

, L. M. Awasthi1,3

, P. K. Srivastava1, S. K. Mattoo

1, D. Sharma

1, P Srivastav

1,

R. Sugandhi1, R. Singh

2, R. Paikaray

3 and P. K. Kaw

1

1

Institute for Plasma Research, Bhat, Gandhinagar-382 428, India 2Advance Technology Center, NFRI, Daejeon, Rep. Korea 3Ravenshaw University, Cuttack-753 003, India


Introduction of strong transverse magnetic field by Electron Energy Filter (EEF) in Large

Volume Plasma Device (LVPD) produces experimental scenario in source region by producing

a strong energetic electron belt, quite similar to the situation prevailing in earth’s

magnetosphere. The coupled magnetic field which comprises of EEF and ambient axial field,

excited loss cone feature from magnetic mirror in the velocity distribution of reflected energetic

electrons. The reflected electrons subsequently excites turbulence, identified as obliquely

propagating Quasi-Longitudinal (QL) whistlers [1-3]. The plasma turbulence exhibits

characteristic features namely, 1) electromagnetic nature, 2) growth time, mstgrowth 1~ , 3) wave

numbers 1

|| 06.0~ cmk and 12.1~

cmk , 4) highly oblique propagation,

0

||

1 87)/(tan

kk , 5) correlation coefficients ze BnC , and

fenC , as 9.0 and 7.0 , and 6)

changing polarization respectively.

These observations may be useful in getting deeper insight into the physical processes taking

place in the magnetosphere, where similar observations are reported when pole bound electron

flux gets trapped in the earth’s magnetic field and suffers loss cone instability generating the QL

whistlers. These investigations may give insight for understanding the role of runaway electrons

in fusion plasmas as are responsible for exciting whistlers. The detailed characterization of QL

whistlers and their energy dependence will be presented in the conference.

References:

[1] R. R. Sharma and Loukas Vlahos, The Astrophysical Journal 280, 405(1984).

[2] O. P. Verkhoglyadova, B. T. Tsurutani, and G. S. Lakhina, J. Geophys. Res. 115, A00F19 (2010).

[3] Henry G. Booker and Rolf B. Dyce, Radio Science Journal of Research NBS/ USNC-URSI, Vol.

69D, No. 4, April 1965.


80

P-27: The breakdown of the weakly-nonlinear regime for kinetic instabil

David Sanz-Orozco and Herbert L. Berk

University of Texas at Austin: Institute for Fusion Studies


The evolution of marginally-unstable waves that interact resonantly with populations of

energetic particles is governed by a well-known cubic integro-differential equation for the mode

amplitude [1]. One of the outcomes predicted by the equation is the so-called “explosive”

regime, where the amplitude grows indefinitely, eventually taking the equation outside of its

domain of validity [2]. Beyond this point, only full Vlasov simulations will accurately describe

the evolution of the mode amplitude. In this work, we study the breakdown of the cubic

equation in detail. We find that, while the cubic equation is still valid, the distribution function

of the energetic particles locally flattens or “folds” in phase space. This feature is unexpected in

view of the assumptions of the theory that are given in [1]. We also derive for the first time the

fifth-order terms in the wave equation, which not only give us a more accurate description of the

marginally-unstable modes, but they also allow us to predict the breakdown of the cubic

equation. Our findings allow us to better understand the transition between weakly-nonlinear

modes and the long-term chirping modes that ultimately emerge [3].

References:

[1] B. N. Breizman, H. L. Berk, M. S. Pekker, F. Porcelli, G. V. Stupakov, and K. L. Wong, Physics of

Plasmas 4, 1559 (1997).

[2] D. Sanz-Orozco and H. L. Berk, Physics of Plasmas 24, 055701 (2017).

[3] H. Berk, B. Breizman, and N. Petviashvili, Physics Letters A 234, 213 (1997), erratum, ibid. 238,

408 - (1998).



81

P-28: What shapes the radial structure of energetic particle induced geodesic acoustic

modes?

Mirjam Schneller1, GuoYong Fu

1,2, Ilija Chavdarovski

3, WeiXing Wang

1, Philipp Lauber

3,

ZhiXin Lu3

1 Princeton Plasma Physics Laboratory, USA

2 Zhejiang University, China

3 Max Planck Institute for Plasma Physics, Germany

Energetic particles are ubiquitous in present and future tokamaks due to heating systems and

fusion reactions. Anisotropy in the distribution function of the energetic particle population is

able to excite oscillations from the continuous spectrum of geodesic acoustic modes (GAMs),

which cannot be driven by plasma pressure gradients due to their toroidally and nearly

poloidally symmetric structures. These oscillations are known as energetic particle-induced

geodesic acoustic modes (EGAMs) [G.Y.Fu’08] and have been observed in recent experiments

[R.Nazikian’08]. EGAMs are particularly attractive in the framework of turbulence regulation,

since they lead to an oscillatory radial electric shear which can potentially saturate the

turbulence.

For the presented work, the nonlinear gyrokinetic, electrostatic, particle-in-cell code GTS

[W.X.Wang’06] has been extended to include an energetic particle population following either

bump-on-tail Maxwellian or slowing-down [Stix’76] distribution function. With this new tool,

we study how the safety factor and temperature profiles (thus the GAM continuum) and

energetic particle orbit width affect the location and radial mode structure of the excited EGAM.

A detailed understanding of EGAM excitation reveals essential for future studies of EGAM

interaction with micro-turbulence.

82

P-29: Comprehensive magnetohydrodynamic hybrid simulations of fast ion driven Alfvén

eigenmodes and fast ion losses in the Large Helical Device

R. Seki 1,2

, Y. Todo 1,2

, Y. Suzuki 1,2

, K. Ogawa 1,2

, M. Isobe 1,2

, and M. Osakabe 1,2

1 National Institute for Fusion Science, Natural Institutes of Natural Sciences, Toki, 509-5292,

Japan 2 SOKENDAI (The Graduate University for Advanced Studies), Toki, 509-5292, Japan


Fast ion driven instabilities such as Alfvén eigenmodes (AEs) are observed in the Large Helical

Device (LHD). The lost fast ions during these instabilities were measured by scintillator-based

lost fast-ion probe [1] and an enhancement of fast ion losses with pitch angle = 30-45 degree

was observed. The magnetohydrodynamic (MHD) hybrid simulation code, MEGA [2], is

applied to the LHD experiment to identify the instabilities and to clarify the process of the fast

ion losses. The temperature and density profiles measured in the LHD, and the equilibrium

magnetic field calculated with the HINT [3] were used in the simulations. The beam deposition

profile was calculated with the HFREYA [4]. As the first step for the analyses of AEs in the

LHD including neutral beam injections (NBI), collisions, and losses, MEGA is benchmarked

against classical fast ion simulation code, MORH [5], in which the higher order Runge-kutta and

spline interpolation are used. The good agreements are found between these codes in the

classical fast ion distribution (Fig. 1).

(a) MEGA (b) MORH

Fig. 1 Comparison of fast ion distribution.

A multi-phase simulation, which is a combination of classical simulation and hybrid simulation

for energetic particles interacting with an MHD fluid, was performed using the MEGA. In the

multi-phase hybrid simulation, the classical and the hybrid simulations are run alternately. It is

found that the stored fast ion energy is saturated due to the interaction with toroidal Alfvén

eigenmodes (TAEs) at a lower level than that of the classical simulation. We will show the

spatial profile of the TAEs and the fast ion redistribution during the TAE bursts. In addition, the

spatial locations and the velocity distribution of lost fast ions will be compared with the lost

fast-ion probe measurements.

References:

[1] K. Ogawa, et al., Nucl. Fusion 52, 094013 (2012).

[2] Y. Todo, et al., Nucl. Fusion 54, 104012 (2014).

[3] Y. Suzuki, et al., Nucl. Fusion 46, L19 (2006).

[4] S. Murakami, et al., Trans. Fusion Technol. 27, 256 (1995).

[5] R. Seki, et al., Plasma and Fusion Res. 5 027 (2010).


83

P-30: Estimation of orbit island width from static magnetic island width, using safety

factor and orbit pitch

Kouji Shinoharaa, Andreas Bierwage

b, Yasuhiro Suzuki

c, Junghee Kim

d,

Go Matsunagaa, Mitsuru Honda

a, Tongnyeol Rhee

d

aNational Institutes for Quantum and Radiological Science and Technology, Naka, Ibaraki,

Japan

bNational Institutes for Quantum and Radiological Science and Technology, Rokkasho, Aomori,

Japan

cNational Institute for Fusion Science, Toki, Gifu, Japan

dNational Fusion Research Institute, Daejeon, Korea


A simple but reliable reduced model for fast ion transport is preferable to minimize the

computation time while maximizing the accuracy of the numerical predictions. In a recent study

of fast ion transport in the presence of a resonant magnetic perturbation (RMP) field in the

KSTAR tokamak [1], we demonstrated that co-passing beam ions generated on the high-field

side were subject to rapid losses (within a few transit periods) due to the combination of two

factors: (i) the large magnetic drift of fast ions across a wide range of magnetic surfaces, and (ii)

resonant interactions between the fast ions and RMP-induced magnetic islands. We recognized

these effects could be more important than RMP-induced magnetic stochasticity.

Here, we propose a method for estimating the widths of "orbit islands" for guiding center orbits

that characterize the radial excursions of passing particles in the presence of static magnetic

perturbations. Given the radial location ψ and width Δψ of a magnetic island chain in

normalized flux space ψ=[0,1], the corresponding location Pφ and width ΔPφ of the orbit island

in the canonical toroidal momentum coordinate Pφ is estimated by relating the safety factor

profile q(ψ) ≈ rBT/RBP to an equivalent orbit pitch parameter h(Pφ) = <rvT/RvP>. Here, <...>

denotes an orbit average, and subscripts "P" and "T" denote the poloidal and toroidal

components of the magnetic field B and particle velocity v. This can be understood by noting

that, in the presence of a static magnetic perturbation (frequency ω=0), the transit resonance

condition is ωT/ωP = mf/nf (n f and m f are integers), where the left-hand side approximately

corresponds to h(Pφ) and the right-hand side to the pitch of the perturbation for a particle. The

method was applied to a KSTAR plasma with RMPs. The error of the estimated orbit island

width lies within 25% of the actual orbit island width obtained from an orbit calculation, even

when a magnetic drift is large, covering about 50% of the minor radius. Moreover, the estimates

obtained with our method are consistent with our previous finding that, in the present case, the

effect of stochastic field structures is negligible, so that the rapid losses of co-passing NB ions

shortly after their injection can be explained by the combined effect of magnetic drifts and

isolated resonant magnetic island structures.

References:

[1] K. Shinohara et al., Nucl. Fusion 56 (2016) 112018


84

P-31: Effects of collisions on the saturation dynamics of TAEs in tokamaks and

stellarators

C. Slaby, A. Könies, and R. Kleiber

Max-Planck Institut für Plasmaphysik, Teilinstitut Greifswald, Wendelsteinstraße 1, 17491

Germany

E-mails of Corresponding Authors: [email protected], [email protected],

[email protected]

Predicting the saturation levels of toroidicity-induced Alfvén eigenmodes (TAEs) is an

important prerequisite in order to assess transport-induced losses of fast ions in future fusion

reactors and in present-day devices. The fast ions resonantly destabilize the mode in the linear

phase. In the non-linear phase, the reaction of the fast ions to the perturbed fields can lead to

particle-ejection from the confinement region.

This paper presents a numerical study of the non-linear saturation dynamics in tokamaks and

stellarators. Special attention is given to the influence that pitch-angle collisions among the fast

ions have in the non-linear regime.

We use the robust perturbative model implemented in CKA-EUTERPE [1] to calculate the

resonant wave-particle interaction in our numerical simulations. The mode structure is pre-

calculated by CKA [2] and remains fixed for the entire calculation. The global, non-linear, gyro-

kinetic, delta-f code EUTERPE is used to calculate the motion of particles in the pre-calculated

field and to compute the energy transfer from the fast ions to the mode. This information is then

used to advance the mode amplitude in time.

The standard ITPA benchmark case [3] is used to numerically confirm the theoretically

predicted scaling of the saturation amplitude with respect to collisionality in tokamaks. Good

agreement between analytical theory [4] and the numerical simulations is found for low enough

collision frequencies ν. For higher collision frequencies, for which the analytical theory is no

longer valid, a different scaling law is found numerically.

We show that using a momentum-conserving collision operator does not change the scaling

significantly for small ν, but is important for high collision frequencies.

The scaling of the saturation amplitude is also investigated in a Wendelstein 7-X high-mirror

configuration. We compare the stellarator results to the ones obtained for tokamaks and point

out similarities and differences.

References

[1] T. B. Fehér, Ph.D. thesis, University of Greifswald (2013)

[2] A. Könies, et al., 10th IAEA TM on Energetic Particles in Magnetic Confinement Systems (Kloster

Seeon, 2007)

[3] A. Könies, et al., 24th IAEA Fusion Energy Conference (San Diego, 2012)

[4] H. L. Berk, et al., Phys. Rev. Lett. 68 (1992) 3563




85

P-32: Simulation of runaway electrons in tokamaks with pellet suppression and instability

effects

D. A. Spong, L. Carbajal Gomez, D. del Castillo Negrete, L. Baylor

Oak Ridge National Laboratory

Runaway electrons are a significant concern for large tokamak devices both due to gradual

acceleration by the Ohmic heating field and the more rapid acceleration and avalanche

production that can occur during major disruptions. We have developed a simulation model

(KORCGC) that follows large number of runaway guiding center (GC) orbits, taking into

account Coulomb collisions along the orbit, recent modifications for partially screened

impurities [1], synchrotron radiation, rippled (3D) fields, and electric field acceleration,

including inductive effects. Applications to pellet suppression experiments have been made and

show similar effects (current/energy decay rates) as the observations. The energy parameters of

runaway pellet suppression and formation fit within the limits of the GC approximation and the

longer time-steps allowed by GC facilitate modeling over relevant timescales. Introduction of

the effects of fluctuating fields from instabilities, such as neutral beam-driven Alfvén modes and

runaway-driven Whistler modes will also be discussed.

References:

[1] L. Hesslow, O. Embréus, A. Stahl, et al., Phys. Rev. Lett. 118, 255001 (2017).

Work supported by U.S. Department of Energy, Office of Science Contract No. DE-AC05-

00OR22725 with UT-Battelle, LLC and the US DOE SciDAC GSEP Center. This research used

the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory and the

National Energy Research Scientific Computing Center which are supported by the Office of

Science of the US Department of Energy under Contract Numbers DE-AC05-00OR22725 and

DE-AC02-05CH11231, respectively.

86

P-33: Fishbones and de-trapping of fast ions during NBH discharges on TCV

L. Stipani, D. Testa, A. Fasoli, M. Fontana, A. Karpushov, C. Marini, L. Porte,

and TCV contributors

Swiss Plasma Center, Association EURATOM – Confédération Suisse, EPFL, Lausanne, CH

Fishbones are well-known m/n=1/1 fast-particle driven modes that have been routinely observed

in many devices. Following the installation of the Neutral Beam (NB) system, capable of

delivering fast ions with energy up to ~30keV, fishbones have also been routinely observed on

TCV. In this paper we report the first TCV measurements of these modes, which cause an

increase in the flux of escaping neutrals from the fishbone resonant energy up to the NB

injection energy. Our analysis shows a clear link between fishbones and fast ion dynamics on

TCV, applicable to other tokamaks.

In TCV fishbones are measured using the high-frequency magnetic probes and the correlation

ECE diagnostic system. The cross-correlation of these two measurements provides information

on the radial Eigenfunction of the mode. In steady-state NB-heated discharges, the fishbone

appears as a quasi-periodic ~1ms burst in the magnetic and CECE data occurring every 7msec to

10msec. The magnetics usually observe the 1st m/n=1/1 harmonic, and also the 2

nd and 3

rd

harmonics, the latter two however not well diagnosed by the CECE. The mode frequency is

Doppler shifted by the toroidal plasma rotation, so that the 1st harmonic appears in the frequency

range between 25kHz and 30kHz, corresponding to a mode frequency in the plasma rest frame

of ~2kHz. The mode is driven by the injected NB ions with a resonant perpendicular velocity

~2keV just slightly supra-thermal for the 1st harmonic. It has a strongly ballooning character,

with a perturbed poloidal field measured by the magnetic probes on the LFS and HFS of

BPOLLFS

~50mG and BPOLHFS

<10mG. The fishbone is also detected in the perturbed radial and

toroidal components of B by the LTCC-3D magnetic sensors recently installed on the LFS,

with typical amplitude BRADLFS

~10mG and BTORLFS

~3mG. Combining the magnetics and

CECE measurements, we find that the 1st harmonic Eigenfunction is peaked at the q=1 surface,

with an estimated amplitude in the plasma core exceeding 800mG.

A steerable compact Neutral Particle Analyzer (NPA) measures, synchronously with the

fishbones, a ~30% increase in the flux of escaping neutrals in the range from slightly supra-

thermal (~2keV) up to the NB injection energy, for four different viewing lines that see mostly

passing particles. This indicates that the fishbone does not cause a redistribution in energy, but

only in velocity and in radial position at essentially constant energy of the injected fast ions, so

that particles previously trapped (thus not seen by the CNPA) have become passing and fall in

the CNPA viewing lines.


received funding from the Euratom research and training program 2014-2018 under grant

agreement number 633053. The views and opinions expressed herein do not necessarily reflect

those of the European Commission. This work was supported in part by the Swiss National

Science Foundation.

87

P-34: Effects of Trapped Energetic-Ion-Driven Resistive Interchange Modes on Deuterium

Beam Ions and Background Plasmas of LHD

T. Bando1, S. Ohdachi

1,2, M. Isobe

1,2, K. Nagaoka

2, Y. Suzuki

1,2, X. D. Du

3, K. Y. Watanabe

2,

Y. Narushima1,2

, K. Ogawa1,2

, H. Tsuchiya2, T. Akiyama

1,2, T. Ido

2, A. Shimizu

2,

M. Yoshinuma1,2

, S. Masuzaki1,2

, T. Ozaki2, R. Seki

1,2, H. Takahashi

1,2, K. Toi

2, M. Osakabe

1,2,

T. Morisaki1,2

, and the LHD Experiment Group2

1SOKENDAI (The Graduate University for Advanced Studies), 322-6 Oroshi-cho, Toki, Japan

2National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshicho,

Toki, Japan 3University of California, Irvine, CA, USA


In hydrogen plasma experiments of the Large Helical Device (LHD), repeated bursty MHD

fluctuations were observed when the plasmas were heated by the perpendicularly (PERP)

injected NBIs. It was found that they are destabilized by the resonance between the precession

motion of helically trapped energetic ions (EPs) in the peripheral region and the resistive

interchange mode having an n/m = 1/1 mode structure [1]. This instability is called trapped

Energetic-ion-driven resistive InterChange modes (EICs).

EICs have been also observed in the recent experimental campaign started from Mar. 2017,

using two deuterium PERP-NBIs. The acceleration voltage and input power of the PERP-NBIs

are respectively increased from 40 keV to 60/80 keV and from 6 MW to up to 9/10 MW,

compared with those in the hydrogen beam campaign. With these intense deuterium beams, the

amplitude of the magnetic fluctuation of each EIC is enhanced by a factor of 2 to 5 while the

EIC bursts are excited less frequently, compared with those observed in the former hydrogen

campaign. The observed strong EICs lead to large drops (~60%) in the total neutron emission

rate. That means substantial amount of trapped EPs produced by the PERP-NBIs are expelled

from plasmas, since the main source of the neutron is in the EP-plasma interaction. Moreover,

large negative potential drop, up to 25 kV, is observed, which is about two times larger than that

in the hydrogen campaign [1]. This indicates generation of very large radial electric field shear

near the plasma edge. Besides, clear increases of the electron temperature and the line integrated

electron density are observed during the EIC. In this study, the mechanism of loss of EPs and

effect on bulk plasmas by EICs are reported in detail based on RF probes, a NPA, the ion

saturation currents on divertors, ECE measurement, etc.

References:

[1] X. D. Du et al., Phys. Rev. Lett. 114, 155003 (2015).


88

P-35: Stochastic diffusion of energetic ions in Wendelstein-type stellarators

A. V. Tykhyy

Institute for Nuclear Research, Prospekt Nauky 47, Kyiv 03680, Ukraine

In optimized stellarators of the Wendelstein type prompt losses of energetic ions in superbanana

orbits are prevented by means of a modification of the magnetic configuration by high β, so that

the contours of the longitudinal adiabatic invariant of locally trapped particles, J = ∮ v‖ dl, are

closed inside the plasma volume [1]. However, magnetic drift leads to the transformation of

some of these particles into locally passing ones and vice versa. This separatrix crossing is

accompanied by a chaotic jump of J, which results in collisionless stochastic diffusion. The

coefficient of this diffusion in Wendelstein-type stellarators was calculated in reference [2]. It

was concluded that collisionless stochastic diffusion is an important mechanism of the loss of

energetic ions in optimized Wendelstein-line stellarators. In particular, it was found that in a

Helias reactor it leads to a significant fraction of fusion α-particles escaping to the wall before

they transfer their energy to the plasma by means of Coulomb collisions.

However, the theory of ref. [2] employed the expression for the non-adiabatic jump of J for a

particle in a slowly changing harmonic electrostatic potential [3, 4, 5]. The applicability of this

expression to behaviour of transitioning particles in stellarator magnetic configurations was

neither proved nor discussed. In this work, we derive the expression for the jumps of J for the

stellarator magnetic field, following the approach of ref. [5], taking into account the asymmetry

between locally passing particles with opposite signs of v‖ due to the presence of the magnetic

field. It is found that, despite using an expression for the jumps of the adiabatic invariant for a

particle in a slowly changing harmonic electrostatic potential, the conclusions of ref. [2] remain

qualitatively valid. However, diffusion calculated using the updated expression is several times

stronger than previous estimates. The difference is especially pronounced for particles that are

close to passing and are just barely transitioning.

References:

[1] Nuhrenberg J., Lotz W., Gori S., Theory of Fusion Plasma (Editrice Compositori, Varenna, 1994)

[2] Beidler C. D., Kolesnichenko Ya. I., Marchenko V. S., Sidorenko I. N., Wobig H., Phys. Plasmas 8,

2731 (2001)

[3] Timofeev A. V., Sov. Phys. JETP 48, 656 (1978)

[4] Cary J. R., Escande D. F., Tennyson J. L., Phys. Rev. A 34, 4256 (1986)

[5] Neishtadt A. I., Sov. J. Plasma Phys. 12, 568 (1986)

89

P-36: Alfven Eigenmodes stability in 3D configurations using a Landau-closure model

J. Varela1, D. Spong

1 and L. Garcia

2

1 Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-8071 2 Universidad Carlos III de Madrid, 28911 Leganes, Madrid, Spain

The aim of this study is to analyze the destabilization of Alfven Eigenmodes (AE) by energetic

particles (EP) during the operation of magnetic confinement devices using a global model. We

use the reduced MHD equations to describe the linear evolution of the poloidal flux and the

toroidal component of the vorticity in a full 3D system, coupled with equations of density and

parallel velocity moments for the energetic particles, including the effect of the acoustic modes,

finite Larmor radius for ions and energetic particles as well as the Landau damping of electrons

and ions. We add the Landau damping and resonant destabilization effects using a closure

relation. We reproduce the TAE activity observed in LHD [Osakabe, M. et al, Nucl. Fusion, 46,

S911, (2006)], the frequency sweeping evolution of the HAE frequency in TJ-II [A. V.

Melnikov et al, Nucl. Fusion, 54, 123002, (2014)], TAE instabilities in W7X [A. Mishchenko,

Nucl. Fusion, 54, 104003 (2014)], RSAE observed in DIII-D reverse shear operations [W. W.

Heidbrink, Nucl. Fusion, 53, 093006, (2013)] and TAE destabilized in DIII-D pedestal during

high poloidal β discharges [Huang J. APS Division of Plasma Physics Meeting 2016, abstract

#JP10.108]. In addition, we compare the results with gyrokinetic simulations performed by GTC

code.

This material based on work is supported both by the U.S. Department of Energy, Office of

Science, under Contract DE-AC05-00OR22725 with UT-Battelle, LLC. Research sponsored in

part by the Ministerio de Economia y Competitividad of Spain under the project Nr. ENE2015-

68265-P.

90

P-37: Single-n versus multiple-n simulations of Alfvénic global modes

G. Vlad1, S. Briguglio

1, G. Fogaccia

1, V. Fusco

1, C. Di Troia

1, E. Giovannozzi

1, X. Wang

2

1ENEA, FSN, C. R. Frascati, Via E. Fermi 45, 00044 Frascati (Roma), Italy

2Max-Planck-Institut fur Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany

This work presents the results of a set of simulations of global Alfvén modes driven by an

energetic particle (EP) population, with the specific aim of comparing single-n and multiple-n

simulations (n being the toroidal mode number). The hybrid reduced O(ε03) MHD gyrokinetic

code HMGC [1] is used, retaining both fluid (wave-wave) and energetic particles nonlinearities

(ε0 being the inverse aspect ratio of the torus). Note also that HMGC retains self-consistently, in

the time evolution, the wave structures as modified by the EP term. Simulations with the

toroidal mode numbers 1≤n≤10 have been considered. A circular, shifted magnetic-surface

equilibrium has been considered, characterized by a large aspect ratio (ε0=0.1) and a parabolic

safety factor profile q(r)=q0+(qa-q0)(r/a)2 with q0=1.1 and qa=1.9. A bulk ion density profile

ni1/q2, in order to have the toroidal gap radially aligned has also been assumed. The

equilibrium (initial) EP distribution function has been considered to be an isotropic Maxwellian,

with a radial density profile nH=nH0 exp(-19.53 (1-ψ/ψ0)2)), TH/TH0=1, ρH0/a=0.01, vH0/vA0=1,

mH/mi=2 (TH0, ρH0 and vH0 are the on-axis EP temperature, Larmor radius and thermal velocity,

respectively, and ψ the poloidal flux function, and ψ0 its on-axis value). For the specific

energetic particle drive considered (nH0/ni0=1.75×10-3

), single-n simulations are either stable

(n=1), weakly unstable (n=2,3) or unstable (n≥4), with n=10 exhibiting the larger growth-rate,

while 4≤n≤7 the largest saturated amplitudes. A variety of modes are observed (TAEs, upper

and lower KTAEs, EPMs). Nevertheless, no appreciable global modification of the EP density

profile is observed after saturation. On the contrary, the multi-n nonlinear simulation, which is

dominated by particle nonlinearities, exhibits larger growth-rates and higher saturation

amplitudes on all the toroidal spectral components considered, and, as a consequence, it results

in a conspicuous broadening of the EP radial density profile at saturation, thus showing an

enhanced radial transport w.r.t. the single-n simulations.

Fig. 2. Total (magnetic plus kinetic) MHD energy

per toroidal mode number n in single-n (dash

lines) and multi-n (solid lines) simulations.

Fig. 3. Multi-n (1≤n≤10) vs. single-n (n=4)

simulation: initial and saturated energetic particle

density profiles.

References:

[1] S. Briguglio, G. Vlad, F. Zonca, C. Kar, Hybrid magnetohydrodynamic gyrokinetic simulation of

toroidal Alfvén modes Phys. Plasmas 2 (1995) pp. 3711-3723.

10-17

10-15

10-13

10-11

10-9

10-7

10

0 100 200 300 400 500 600

Wtot,n

t/A0

single-n, n=1

single-n, n=2

sinlge-n, n=3

single-n, n=4

single-n, n=5

single-n, n=6

single-n, n=7

single-n, n=8

single-n, n=9

single-n, n=10

multiple-n, n=1

multiple-n, n=2

multiple-n, n=3

multiple-n, n=4

multiple-n, n=5

multiple-n, n=6

multiple-n, n=7

multiple-n, n=8

multiple-n, n=9

multiple-n, n=10

-5

0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1

nH/n

H0

r/a

t/tA0

=0

t/tA0

=345

(multi-n)

t/tA0

=570

(single-n, n=4)

91

P-38: Two-mode dynamics of phase-space holes and clumps in systems near marginal

stability

B. J. Q. Woods1, B. N. Breizman

2, and R. G. L. Vann

1

1 York Plasma Institute, Department of Physics, University of York, York YO10 5DD, U.K.

2 Institute for Fusion Studies, The University of Texas, Austin, TX 78712,USA


The creation and subsequent nonstationary frequency evolution of marginally-unstable modes

have been observed in a wide range of fusion devices. This behaviour has been successfully

explained, for a single mode, in terms of phase-space structures known as a “hole” and “clump”

(i.e. a localised decrease and increase compared to the background distribution, respectively).

The frequency associated with these structures evolves with a characteristic behaviour

tdw dµ due to a combination of adiabatic conservation of the distribution function within the

hole/clump and slow energy loss via dissipation. The existence and behaviour of these modes is

important because they show that it is possible for a resonant wave-particle interaction in a

tokamak to lead to substantial fast particle transport even in the case of only weak instability.

In this contribution we study the interaction of two modes which are nearby in phase-space, one

of which is marginally-unstable and one of which is marginally-stable. We measure the impact

of the pair of modes in terms of the total energy extracted from the system via the dissipative

channel during a single burst and show that under certain circumstances it can be substantially

greater than might otherwise be expected. In particular, we study the evolution of the

marginally-unstable mode and its interaction with the marginally-stable mode. We find that the

phase space perturbation caused by the first mode can nonlinearly destabilise the second

(otherwise stable) mode and, moreover, that this interaction can lead to a substantial increase in

the total lost energy. We show how this lost energy depends on both the distance between

modes and the mode dissipation rate – more specifically, we find that there is an “optimum”

mode separation for which the energy loss is maximised, beyond which the energy loss drops

off rapidly. This behaviour demonstrates that stable modes, perhaps rather counter-intuitively,

may act to enhance rather than suppress energy loss from the system.

This work was partly funded by the UK Engineering and Physical Sciences Research Council.


92

P-39: Fishbone oscillations in EAST

Liqing Xu, Liqun Hu, Yi Yuan, Yingying Li, Guoqiang Zhong, Haiqing Liu, Kaiyun Chen,

Tonghui Shi and Yanmin Duan

Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China


Fishbone oscillation was observed in EAST neutral beam injection plasma. This 1/1 typical

internal kink mode travels in the ion-diamagnetism direction in poloidal section with a rotation

speed close to the ion diamagnetic drift frequency. High thermal plasma beta and amounts of

energetic ions are necessary for mode developed. The born frequency of fishbone oscillation is

the ion diamagnetic drift frequency and the frequency chirping down in the linear phase is due

to the drop of ion diamagnetic drift frequency. The excitation energy of oscillation is thermal

plasma pressure gradient, however, the nonlinear growing of fishbone oscillation is related to

energetic ions.

Fig. 1. Typical fishbone oscillations in EAST high 𝛽𝑃NBI shot #71322. (a)- Core SXR and 𝛽𝑃; (b)- NBI

power𝑃𝑁𝐵𝐼; (c)- FB-O frequency spectrum

mailto:[email protected],%[email protected]

93

P-40: Experimental Observation of Energetic Particle Induced Geodesic Acoustic Mode in

EAST Tokamak

Ming Xu, Jizong Zhang, Yanmin Duan, Tonghui Shi, Songtao Mao, Shiyao Lin, Liqun Hu, and

the EAST Team

Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP), Hefei 230031, China


The GAMs are the oscillating zonal mode structures that are unique in toroidal plasmas [1], with

an m/n=0/0 potential structure, m/n=1/0 pressure fluctuation (up-down anti-symmetric), and

m/n=2/0 magnetic fluctuation [2]. Recent theory and experiment has proven that energetic

particles can excite new branch GAM instability [3-5] with frequency lower than the standard

GAM frequency. The dynamics of energetic electrons has the same roles as energetic ions to

excite the EGAM instability, and one example of simulation has displayed the processional

resonance of trapped fast electrons is responsible for BAE excitations has been done by GTC

[6].

EGAM instability excited by energetic ions during the injection of NBI has been observed in

EAST, and the EGAM is more easily observed during the tangential injected of NBI beam that

parallel to the direction plasma current. Some results for the EGAM can summarized as

following:

(1) The structure of EGAM has up-down anti-symmetric with phase shifted by π that located at

ρ~0.6(q~3) with radial width ∆𝑟 𝑎⁄ ~0.2 − 0.3 , and the mode number is m=2/ n~0 that

measured by edge magnetic pickup probes, where m, n are poloidal and toroidal mode number

respectively. (2) The radial width of EGAM is not only has strong relationship with the drift

orbit width of energetic ions, but also relied on the plasmas elongation in EAST. (3) The EGAM

is coexisted with low frequencies mode(LFM: f=4-5kHz with m ≥ 4/ n~-2), and is terminated

with the burst of strong tearing modes (TMs: f=2.3kHz with m=-2/n=1), where the location for

LFM and TMs are ρ < 0.2 and ρ = 0.3 − 0.4 respectively, and the propagation direction for

LFM and TMs are fully inverted (the direction for LFM is anti-parallel to the plasma current in

toroidal and ion diamagnetic drift in poloidal).

One possible situation is that weak or reversed magnetic shear is formed during the EGAM

instability, and the calculation for other kinds of EGAM-like instability during the runaway

plasmas with electron densityne < 0.5 × 1019𝑚−3 also demonstrated the lower magnetic shear

is easily for the excitation of the instability for the condition of trapped energetic electrons.

References:

[1] N. Winsor, J. L. Johnson, and J. M. Dawson, Physics of Fluids 11, 2448 (1968).

[2] D. Zhou, Physics of Plasmas 14, 104502 (2007).

[3] G. Y. Fu, Physical Review Letters 101, 185002 (2008).

[4] R. Nazikian et al., Physical Review Letters 101, 185001 (2008)

[5] Z. Qiu, F. Zonca, and L. Chen, Physics of Plasmas 19, 082507 (2012).

[6] J. Cheng et al., Physics of Plasmas 23 , 052504 (2016).


94

P-41: Sawtooth mixing of alphas, knock-on D, T ions and its influence on NPA spectra in

ITER plasma

F.S. Zaitsev1,4

, N.N. Gorelenkov

2, M.P. Petrov

3, V.I. Afanasyev

3, M.I. Mironov

3

1Scientific Research Institute of System Development, Russian Academy of Sciences

2Princeton Plasma Physics Laboratory, Princeton University, USA

3A.F. Ioffe Physical-Technical Institute, St. Petersburg, Russia

4Moscow State University, Russia

An important direction of ITER plasma research implies a detailed study of plasma sawtooth

activity and its influence on fast ions behavior. As it was observed in DT experiments on TFTR

sawtooth activity can lead to significant redistribution of fast ions including fusion alphas in the

minor radius and eventually to their losses [1]. Consequently, accounting for such effects in

ITER seems to be necessary for maintaining the optimal reactor performance.

The model of sawtooth plasma mixing was proposed by B.B. Kadomtsev in 1975. Later that

model was advanced by many authors. However, the transition to study the sawtooth mixing

phenomena in ITER requires further generalization of the model to the case of the plasma non-

circular magnetic surfaces, its arbitrary aspect ratio, significant deviations of drift trajectories

from the flux surfaces, and arbitrary helicity of ideal mode perturbation. Such generalization is

developed in our contribution.

An effective tool for fast ions studies in ITER will be the system of Neutral Particle Analyzers

(NPA) [2], since it allows direct measurements of fast ions distribution function inside the

plasma. NPA registers the so-called Line of sight Integrated Distribution (LID) [3], which gives

the information about the energy distribution of ions (energy spectrum). Adequate LID

calculation requires accounting for a number of complicated kinetic effects: deviations of drift

trajectories from the flux surfaces; Coulomb collisions (diffusion and friction in velocity, pitch-

angle scattering, neoclassical radial transport, etc.); sources and sinks of particles; nuclear elastic

scattering (NES); plasma instabilities and oscillations, and etc. This is included in the FPP-3D

code simulations [3].

ITER plasma with 15 MA inductive current scenario was used for the modeling of He4, D and T

sawtooth mixing calculated by the FPP-3D code. It accounts for sawtooth mixing and D, T NES

on He4. It was found that mixing can significantly change the He

4 radial distribution. The D and

T NPA spectra and their sensitivity to sawtooth mixing are also calculated. Those spectra were

analyzed with the respect of the NPA ability to measure D/T fuel isotope ratio in ITER plasma

core in the presence of sawteeth.

References.

[1] N.N. Gorelenkov, R.V. Budny, H.H. Duong, R.K. Fisher, S.S. Medley, M.P. Petrov, M.H. Red. Nucl.

Fusion. 1997, v. 37, N 8. p. 1053-1066.

[2] V.I. Afanasyev, F.V. Chernyshev, A.I. Kislyakov, S.S. Kozlovski, B.V. Ljublin, M.I. Mironov, A.D.

Melnik, V.G. Nesenevich, M.P. Petrov, S.Ya. Petrov. Nuclear Instruments and Methods in Physics

Research. 2010, A 621, p. 456–467.

[3] F.S. Zaitsev. Mathematical modeling of toroidal plasma evolution. English edition. MAKS Press,

2014, 688 pp.

F.S. Zaitsev research was partly funded by grant I.33 of Presidium of Russian Academy of

Sciences.

95

P-42: Plasma equilibrium with fast ion orbit width, velocity anisotropy and toroidal flow

effects

L.E. Zakharov1, N.N. Gorelenkov

2

1LiWFusion, P.O. Box 2391, Princeton

2Princeton Plasma Physics Laboratory, Princeton University

The computation of accurate plasma equilibrium in present day fusion devices is motivated by

applications of auxiliary neutral beam injection (NBI) heating which generates high betas of

Energetic Particles (EP) such as beam ions. Robust prediction of beam ion confinement in the

presence of Alfvénic instabilities depends on the accuracy of used equilibrium model. AE

eigenfrequencies and stability depend on such equilibrium properties as the magnitude of the

Shafranov shift, plasma pressure gradient and plasma rotation.

We present a model to solve the equilibrium problem including the aforementioned effects in

the presence of finite drift orbit radial width (FOW) of EPs. The formulation is novel and shows

that FOW effects are on the same order as the plasma pressure anisotropy.

Employed framework is built upon the ESC equilibrium q-solver [1]. The plasma pressure

anisotropy σ , is included through EP pressure parallel component,

1− σ= B− 1

∂ Ph∥/∂ B , (1)

which also implies the poloidal dependence of the perpendicular pressure since

σ≈ 1+ 4π(Ph⊥− Ph∥)/ B2

.

The expression of the parallel pressure component in the presence of FOW is given in a novel

way. Namely, for single pitch angle passing ions, λ= λ0 , we find

Ph∥(Ψ , B)=3β0 BB0

8 π √1− λ 0

B

B0[F (Ψ)±

2

3ρL Bφ R FΨ(1−

B0

B )],

(2)

whereas for trapped ions

Ph∥(Ψ , B)=3β0 BB0

8 π √1− λ 0

B

B0[F (Ψ)−

2

3ρL Bφ R FΨ

B0

B √1− λ0

B

B0]

,

(3)

where Ψ is the normalized poloidal flux (averaged over the drift orbit is denoted with the upper

bar), ρL is EP Larmor radius, and F is the radial dependence of EP distribution function.

The EP pressure anisotropy formulation is based on the moments of the velocity distribution

function. Anisotropic beam ions accompanied by plasma rotation are addressed in various

applications involving for example the stability of Alfvenic and internal kink modes. The

anisotropy and rotational effects could be treated separately or together depending on the

problem.

References:

[1] L. E. Zakharov. A. Pletzer, Phys. Plasmas, v. 6 (1999) 4693.

96

P-43: Excitation of whistler waves and magnetized plasma waves by runaway electrons in

tokamaks

Chang Liu1, Eero Hirvijoki

1, Dylan P. Brennan

2, Amitava Bhattacharjee

1,2

1

Princeton Plasma Physics Laboratory 2

Princeton University


Runaway electron is a critical area of current study for tokamak disruptions. In both quiescent

runaway electron experiments (QRE) and post-disruption experiments, the whistler wave

instabilities have been observed and are closely associated with the abrupt growth of electron

cyclotron emission (ECE) signals from runaway electrons [1]. In order to understand this

connection and how the whistler wave instabilities affect the runaway electron distribution in

momentum space, a self-consistent kinetic simulation of runaway electrons, including both the

secondary generation and the diffusion effects from the excited modes, is required.

Here we report results of a newly developed simulation code for runaway electron distribution

evolution and the growth of unstable whistler waves, including the diffusion effect through the

quasilinear model [2]. With the help of this new tool, we find that three different branches of

waves can be excited by runaway electrons in a QRE experiment. The low frequency whistler

waves and the high frequency magnetized plasma waves are excited by runaway electrons in

high energy regimes and those in low energy regimes respectively. The Landau damping of

them, which happens at the same energy regime due to the close phase velocities, connects the

excitation of the two branches of waves. This effect is observed in experiments, where both the

synchrotron radiation signals and the ECE signals show cyclic behaviors [2]. In addition, we

find a third branch of waves, which are very low frequency whistler waves propagating almost

perpendicular to the magnetic field, can be excited by the bump-on-tail distribution of the

runaway electrons. These whistler waves have just been observed in recent DIII-D QRE

experiments, which is by the first time that whistler waves have been observed in tokamak

experiments.

These new findings can help explain several runaway electron experimental results in different

tokamaks, and can be used to estimate the effect of whistler wave instabilities in runaway

electron mitigations in ITER.

References:

[1] C. Paz-Soldan, R.J.L. Haye, D. Shiraki, R.J. Buttery, N.W. Eidietis, E.M. Hollmann, R.A. Moyer,

J.E. Boom, I.T. Chapman, and J.E.T. Contributors, Nucl. Fusion 56, 056010 (2016).

[2] A.N. Kaufman, The Physics of Fluids 15, 1063 (1972).

[3] R.J. Zhou, L.Q. Hu, E.Z. Li, M. Xu, G.Q. Zhong, L.Q. Xu, S.Y. Lin, J.Z. Zhang, and the E. Team,

Plasma Phys. Control. Fusion 55, 055006 (2013).


97

P-44: Manipulating Energetic Ion Velocity Space to Control Instabilities and Improve

Tokamak Performance

D.C. Pace

General Atomics, P.O. Box 85608, San Diego, CA 92186-5608

The first-ever demonstration of independent current (I) and voltage (V) control of high power

neutral beams in tokamak plasma shots has successfully reduced the prevalence of instabilities

and improved energetic ion confinement. Energetic ions drive Alfvén eigenmode (AE)

instabilities through a resonant energy exchange that can increase radial diffusion of the ions,

thereby reducing beam heating and current drive efficiency. This resonance is incredibly

sensitive to the ion velocity and orbit topology, which then allows changes in beam voltage

(keeping the injected power constant through compensating changes in current) to remove

nearly all instability drive. The implementation of temporal control of beam current and voltage

allows for a reduction in the resonant energetic ion velocity space while maintaining the ability

to inject maximum power. Low confinement (L-mode) plasmas demonstrate a nearly complete

avoidance of AE activity in plasmas with 55 kV beam injection compared to the many AEs that

are observed in plasmas featuring similar total beam power at 70 kV. Across the experimental

range of beam settings, resulting increases in beam divergence have been inconsequential. High

performance steady-state scenarios featuring equilibria that are conducive to dense arrays of

Alfvén waves benefit the most from instability control mechanisms. One such scenario, the so-

called high qmin scenario, demonstrates improved confinement and equilibrium evolution when

the injected beam voltage begins at lower values (i.e., fewer resonances) and then increases as

the plasma reaches its stationary period. These results suggest a future in which plasma

confinement and performance is improved through continuous feedback control of auxiliary

heating systems such that the energetic ion distribution is constantly adapted to produce an

optimal plasma state.


98

P-45: Low-Frequency Fishbone Driven by Passing Fast Ions in Tokamak Plasmas

G. Y. Fu1,2

, L. M. Yu3, F. Wang

4

1Princeton Plasma Physics Laboratory, Princeton, NJ, USA

2Zhejiang University, Hangzhou, China

3East China University of Science and Technology, Shanghai, China

4Dalian University of Technology, Dalian, China

Energetic particle-driven fishbone instability is commonly observed in tokamak and stellarator

plasmas with NBI and/or RF heating after its discovery in the PDX tokamak [1]. In PDX, with

perpendicular NBI, it was understood that the fishbone instability was driven by trapped

energetic ions through precessional drift resonance [2, 3]. The mode frequency is either

determined by energetic ion precessional drift frequency for the energetic particle mode (EPM)

branch [2] or the thermal ion diamagnetic drift frequency for the *i branch [3]. In the PBX

tokamak, the fishbone instability driven by passing fast ions was first reported. The instability is

driven by the parallel wave particle resonance =k||v||=(1-p/q)v||/R, where p is an integer and q is

the safety factor. The passing particle-driven fishbone has two branches: the low frequency

branch (p=1)[4] and the high frequency branch[5,6]. In particular Betti and Freidberg showed

that the low frequency fishbone can be driven unstable by passing fast ions due to effects of

finite orbit width. The mode frequency is determined by the thermal ion diamagnetic drift

frequency. In this work, the theory of the low frequency fishbone [4] is extended to the EPM

branch. It is shown analytically that an EPM-like low frequency fishbone can be excited by

passing energetic ions. The mode frequency is determined by energetic particle’s transit

frequency via parallel wave particle resonance condition. The analytic results have been verified

by numerical calculation and are consistent with the recent observation of low frequency

fishbone instability in the HL-2A tokamak.

References:

[1] K. McGuire et al., Phys. Rev. Lett. 50, 891 (1983).

[2] L. Chen, R.B. White and M.N. Rosenbluth, Phys. Rev. Lett. 52, 1122 (1984)

[3] B. Coppi and F. Porcelli, Phys. Rev. Lett. 57, 2272 (1986)

[4] R. Betti and J.P. Freidberg, Phys. Rev. Lett. 70, 3428 (1993)

[5] S. J. Wang, Phys. Rev. Lett. 86, 8286 (2001)

[6] F. Wang, L.M. Yu, G.Y. Fu, and W. Shen, Nucl. Fusion 57, 056013 (2017)