burning plasma research on iter - iter - the … for iter d-t plasma ∆∆∆∆ti due to 2nd...

Burning Plasma Research on ITER

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R.J. Hawryluk

24th IAEA Fusion Energy Conference

October 9, 2012

The views and opinions expressed herein do not necessarily reflect those of the ITER Organization.


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nTechnical Progress Enabled TFTR and JET to Begin

Studying D -T Burning Plasmas

• Current experiments are setting the stage for the I TER Research Program enabling:

• Development of burning plasma conditions and study of burning plasmas

Fus

ion

Pow

er (

MW

)


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First High Power D -T Experiments Will Generate More Fusion Energy than All Previous

MFE Fusion Experiments

• For comparison, JET produced 0.7 GJ and TFTR 1.7 GJ during their DT campaigns.

• ITER will provide a facility to study the physics o f burning plasmas

0

5

10

15

20

25

0

100

200

300

400

500

0 100 200 300 400 500 600 700t, s

Ip

Pfus

Paux

Q=10 scenario250 GJ

Y. Gribov


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nBurning Plasmas in ITER Will Require an

Unprecedented Integration of Scientific Issues

Nonlinear interaction of turbulence, wall-interacti on, external sources, fusion reactivity, macroscopic instabilities.Strong coupling between the plasma and “external” sys tems especially plasma-wall interactions associated with:

Erosion, tritium retention, high heat loads, transi ent events

MHD Instabilities

R. Politzer

Magnetic Shaping


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What Questions Will Be Addressed in the Burning Plasma Research Program?

Transport and Turbulence– Isotope Effects

• ICRF Heating

Alpha-particle Physics

• Stability and Integrated Modeling

• Plasma-boundary Interface– See D. Campbell’s talk


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JET D-T Elmy H-mode Experiments Consistent with ITER Scaling

• What is the role of the pedestal and the core?

JET0.8 NBI ICRH

0.7

0.6

HDD–TT

0.5

0.4

0.3

0.2

0.1

00 0.1 0.2

τITERH–EPS97(y) (s)

τ th

(s)

0.3 0.4 0.5 0.6 0.7 0.8JG

98.3

05/2

a

• τth ∝ <A>0.16±0.06

w

r/a 1

Pedestal

Core Tra

nspo

rt b

arrie

r

JG98

.325

/4c

Cordey


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nStored Energy Associated with Pedestal

Increased with <A> in JET

• Wped ∝∝∝∝ <A>0.96

• Power loss by ELMs decreases• Stored energy is a complex interplay of access to

H-mod and pedestal stability – See Urano’s paper

BhatnagarCordey


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nIon Thermal Conductivity Changes with <A>

Depending on Operating Regimes

• In JET H-modes, χχχχi scaling in the core consistent with gyro-Bohm.

– τthcore ∝<A> -0.16±0.1

χI ∝ <A>0.73±0.4

Cordey

τEthermal ∝ <A>0.89±0.1

χitot ∝ <A>-1.8 ±0.2

In TFTR Supershots, confinement dramatically improved in the core and χχχχi decreased

S. Scott, M. Zarnstorff

ITG model with radial electric field reproduced the T i(r) profile, (Ernst)

JET TFTR

factor of 2


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Isotope Effect on Confinement Varied Widely Depending on Operating Regime

• Diversity of scalings challenges theory and – gyro-Bohm scaling: <A>-0.2

• ITER scaling for ELMy H-mode: ττττEthermal ∝∝∝∝ <A>+0.19

S. Scott, S. Sabbagh, C. K. Phillips


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Power Threshold on JET Going fromL to H -mode Shows Favorable Isotope Scaling

• Ploss ∝ ∝ ∝ ∝ <A>-1

JETHydrogen

2

PLO

SS (

MW

)

4

0.83ne1.12Bt

0.69R2

6 800

2

4

6

8

Deuterium

Tritium

DT

wall loading seriescryompump off25:75 DT

10:90 DT

ER

98.0

26

Righi


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Higher Neutral Beam Power Required for Enhanced Reverse Shear (ERS) Transition in D -T

• Challenge for theory: same or lower threshold expec ted• Was this a transport effect or a consequence of the beam

deposition profile being different?

M. Bell, S. Scott, M. Zarnstorff


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Summary of Isotope Effects on Confinement

• H-mode isotope scaling studies on JET, together with the worldwide physics database, provide a good technical basis for baseline operation of burning plasma experiments.

– Isotope scaling for τE and power threshold.

• Understanding of isotope scaling is incomplete since it depends on operating regime.

– Not consistent with naive turbulence theory scaling– What is the role of radial electric field shear in the different regimes?– What are the implications for advanced operating modes?

• Power threshold for internal barrier formation incr eased with <A>.

– What are the implications for advanced operating regimes in ITER?


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nJET Demonstrated Successful Deuterium

Minority Heating of Tritium Plasmas• Record Q DT for steady-

state operation.– deuterium energy

optimized– Not optimal for high QDT

• Strong ion heating observed with 3He

– Absorption weaker with 2ΩΤ

– Recommended scenario for ITER

• Studied tritium minority heating.

Eriksson, Start


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nICRF Successfully Heated D -T Supershot

Plasmas in TFTR

• Power deposition calculations in good agreement wit h experiment.

ΩcHe3 to ΩcT transition heating regime shown to give efficient heating suitable for ITER D-T plasma

∆∆∆∆ Ti due to 2nd harmonic tritium heating

∆∆∆∆ Te due to direct electron and 3He minority ion heating

Ti (

keV

)

2.5 3.0 3.5

30

20

10

no RF

2.5 3.0

2

4

6

8

10

R(m)

Te

(ke

V)

with RF

no RF

with RF

magnet ic axis

magnet ic axis

R(m)

G. Taylor, J. R. Wilson, J. Hosea, R. Majeski, C. K. Phillips


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Implications of ICRF Heating and Current Drive Studies

Fundamental heating and current drive physics for I CRF has largely been established for D-He 3 minority and second harmonic tritium heating experiments.

Technology and coupling issues need to be further addressed for optimum ICRF application to ITER.

Antenna power density limited by voltage standoff/coupling resistance.

Evaluating installing gas feeds near the ICRF antenna.


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Alpha-particle Physics Studies

• MHD Quiescent– Alpha-particle heating

• MHD Affects on Alpha Confinement

• Alpha-Particle Induced MHD Activity


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nAlpha-Particle Parameters in TFTR/JET

Sufficient to Begin Study of Alpha-Particle Physics

A. Fasoli

TFTR JET ITERPfusion(MW) 10.6 16.1 400pα(0) (MW/m3) 0.28 0.12 0.55βα(0)% 0.26 0.7 1.2–R•grad(βα)% 2.0 2.3 4.0Vα(0)/VAlfvén(0) 1.6 1.6 1.9


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nClassical Alpha Particle Behavior was Confirmed for

Normal Shear (Supershot) Discharges

2.0 2.5 3.00.0

1.0

2.0

3.0

(101

7/m

2 /se

c)Measured

(neutron collimator)

beam-thermal

beam-beam

Thermal

Total

Radius (m)

Cho

rdal

DT

neu

tron

em

issi

on

• Alpha birth rate and profile agreed with modeling.- Neutron flux in good

agreement with calculations based on plasma profile in normal shear discharges.

• Escaping alpha flux at 90 o

detector was consistent with classical first orbit losses

R. Budny, L. Johnson S. Zweben, D. Darrow

TFTR


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nConfined Alpha-particles Were Well Confined in

Normal Shear (Supershot) Discharges

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0 0.2 0.4 0.6 0.8 1

Hel

ium

Den

sity

(x1

016 m

-3)

r/a

No Transport

DHe, VHe from gas puffDat a

4.75 s

Confined alphas in the plasma core showed classical slowing down spectrum .

Alpha particles were well confined.

0 ≤≤≤≤Dαααα≤≤≤≤ 0.03 m2/s

Rapid ash transported from the core to the edge in supershots. (DHe/χχχχD ~ 1

R. Fisher, S. Medley, M. Petrov R. Fonck, G. McKee, B. Stratton E. Synakowski

ITER will extend these results especially ash build up.

TFTR


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Stochastic Ripple Diffusion Affects Confinement of Deeply Trapped Particles

• FPPT includes modeling of stochastic ripple diffusi on.• Heat deposition due to ripple loss of fast ions ima ged on JT60U.• Recent measurements of fast ion loss on DIII-D expe riments used

to simulate the magnetic field from the ITER Test B lanket are in good agreement with predictions.

Major Radius (m) Major Radius (m)

TFTR

Medley, Redi


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Initial Evidence of Alpha-particle Heating on TFTR and JET

• Alpha heating ~15% of power through electron channel .

• Palpha /Pheat ~12%- 30-40% through the

electron channel

• Comprehensive study of alpha heating requires highe r values of Palpha /Pheat .

G. Taylor, J. Strachan

T e(D

T)

-T e

(D)

(keV

)T e

(R)

(ke

V)

P. Thomas, et al.

TFTRT e

(R)

(ke

V)

T e

(R)

(ke

V)

T e

(R)

(ke

V)

∆Te(

0) (

keV)

Pα (MW)

JET


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nInteraction of External Kink/Peeling Modes with

Alpha Particles Observed at JET.

(G. A. Cottrell et al., NF 33, 1365 (1993) ) .

Bursts of the n=1 outer mode, an edge MHD mode interpreted as an external kink/peeling mode, were triggered at a critical alpha particle density as indicated by the ion-cyclotron emission diagnostic.- Is the outer mode ejecting

the edge alphas?- Are the alphas contributing

to triggering the outer mode?

M.F.F. Nave


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nMHD Activity can Cause Enhanced Transport

of Alpha Particles

• Sawteeth caused a large radial redistribution of alpha particles

• Strong toroidal anisotropic loss apparent as NTM mode was rotating.

• Enhanced loss also observed due to: - disruptions - kinetic ballooning modes, sawteeth

R. Fonck, G. McKee, B. Stratton

D. Darrow, S. Zweben


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nTAEs Driven by Neutral Beam or ICRF

Fast Ions Caused Substantial Fast Ion Losses

• In normal shear D-T discharges, TAE was stable on TFTR as well as on JET.

Input Power (MW)1 10 205

10-8

10-7

10-6

10-5

10-9M

ode

Am

plitu

de [B

θ/B

0]~

0.01

0.10

1.00

10.00

100.0Lo

ss F

ract

ion

(%)

- NBI driven TAE

- ICRF driven TAE

D-T experiments

E. Fredrickson, K. L. Wong, D. Darrow

TFTR


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nTFTR Alpha-particle Physics Studies in

Reversed Shear Discharges Resulted in New Discoveries.

2.00

PNBI(MW)

TIME(s)NBI off

βα(0)0

Neutral Beam Injection

10-3

3x10-2

2.5TIME(s)

3.0

BB

~n=4

n=5n=3

n=2

2.8 2.9 3.00

6 x10-9

0

25

103101

β(0)“Damping”

“Drive”

“Response”

wall

T

10 -5

10 -4

10 -3

10 -2

10 -1

0 0.1 0.2 0.3 0.4 0.5 0.6

Alp

ha S

igna

l (a.

u.)

r/a

0.53 MeV and 1.71 MeV with TAE

0.53 MeV and 1.71 MeVno TAE

• Alpha-driven TAE (subsequently identified as Cascade Modes) were observed.

• TAEs redistributed deeply trapped alpha-particles

• Neutron emission in D-T enhanced reverse shear disc harges disagreed with TRANSP analysis in some shots by fac tors of 2-3

–Source of discrepancy was not identified.R. Nazikian, Z. Chang, G. Fu S. Medley, M. Petrov,


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141562

Beam Injection Timing in DIII-D Reversed Shear

Also Alters Mode Stability

141559

NBI NBI

141562 • Injection at 300 ms shows

clear TAEs and RSAEs

– Up to 50% neutron deficit

relative to classical

TRANSP predictions due

to fast ion transport

• Delaying beam injection

until 500 ms alters current profile (still RS) NO AEs

– With no AEs neutron

emission is classical

• PPPL-IFS Quasilinear

Model is in quantitative

agreement in similar

discharges

– H. Berk TH/4-1M. A. Zeeland


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Sea of Alfven Waves Calculated to be Marginally Unstable in ITER

• PPPL/IFS quasilinear model predicts that alpha parti cle losses are acceptable in normal shear discharges.

• Further work required to assess reversed shear or e levated q minoperating regimes.

Gorelenkov


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nSteady-state Operating Scenario is a Complex Interp lay

between Stability, Transport and Alpha Physics

F. Poli

Ideal MHD stability constrains steady-state plasmas to operate with moderate ITBs at mid-radius and with q min>2

MHD stability favors H&CD schemes with off-axis dep osition @ r>0.5- ECRH upper launcher- LH heating and current drive

Ballooning

weakly unst.

Balloon.

n=1 w/o wall


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33MW NB+20MWEC+20MWLH

0

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100

Pow

er (

MW

)

200 400 600 800 10000

5

10

Cur

rent

(M

A)

time (s)

EC, LH

Ref: IP=8.0MA

PαNB

TOTAL

NI

BSNB

EC LH

• Reverse shear in the core is necessary to trigger and sustain ITBs– Obtainable with the day-one heating mix,– However INI~6 and Q<2– qmin<2, n=1 unstable without wall

• A broad current distribution, like that obtained with EC+LH– sustains ~8MA (non-inductive)– achieves Q~3– qmin>2, MHD stable

• Alfven instabilities are likely to be more unstable than in normal shear.– Will that be a positive or negative effect?

Transport Simulations Indicate that EC +LH is Promising towards Steady-state Operation

F. Poli


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Sawteeth Control Requirements in ITER

• Natural sawtooth period in ITER predicted to be approximately same as that required to trigger NTMs

– Empirical scaling

• Stabilizing effects of alpha particles likely to exacerbate by further stabilizing sawteeth

• Recent experiments have determined various methods to obtain shorter sawteeth

– AUG, DIII-D, JET, MAST, TCV, Tore Supra

Chapman et al., ITR/P1-31 IT Chapman et al, Nucl Fusion, 50, 102001 (2010)

βN at which an NTM is triggered by a sawtooth v sawtooth period for an ITER-like subset of discharges. Empirical scaling predicting ITER range is overlaid


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Kinetic resistive wall mode (RWM) stability contours

• Alpha particles can stabliize RWMs

• Significant Re(δWK), but nearly independent of ωφ

• Energetic particles are not in mode resonance

ITER Steady-state Scenario May Benefit from Alpha-Particle

Stabilization of RWM instabilities

γτw contours vs. βα and ωφ

unstable

stable

exp

ect

ed

ωφ

expected

βα

J.W. Berkery, S. Sabbagh, R. Betti


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• Assess the requirements for burn control on ITER– ITER is expected to be globally stable operating in the high

temperature regime– In general, depends on the global scaling of confinement with power.– Can internal transport barriers be triggered by alpha heating?

• May require rapid control techniques.

• Possible actuators:– Heating power– Fueling

• Lower density operation may increase the heat load to the divertor

• Greenwald limit may limit increasing the density– Impurity injection

• Burn Control is part of a much broader issue –– Discharge control and response to faults including disruptions.

Burn Control Can be Assessed in ITER


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nCompatibility with Plasma-Boundary Interface

Will Be One of the Most Challenging Aspects of the D-T Campaign

• Long pulse, high heat flux operation can result in erosion or local damage.

– Development of high recycling divertor, ELM and Disruption Mitigation are critical issues.

– What will be the optimum tradeoff between plasma performance and successful operation of the plasma-wall components?

• Dust has not been an issue in current experiments b ut there will be safety restrictions on ITER

• Tritium retention in graphite based on JET and TFTR experiments would be a serious concern.

– TFTR tiles 16% retention– JET 12% retention

• Results from JET with ILW are very encouraging– ITER will provide a critical assessment


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The Burning Plasma Research Program on ITER will Be Exciting

• Results from TFTR and JET together with the results from the world-wide community has

– Provided solid design basis for a burning plasma experiment.– Experience on TFTR and JET D-T experiments is that new

physics will emerge in ITER

• Full potential and consequences of alpha heating have not been explored!

burning plasma research on iter - iter - the … for iter d-t plasma ∆∆∆∆ti due to 2nd...

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