fast ion measurements by collective thomson...

Fast ion measurements by collective Thomson scattering in TEXTOR and ASDEX Upgrade and proposal for the ITER CTS system S.B. Korsholm, H. Bindslev, V. Furtula, F. Leipold, F. Meo, P. K. Michelsen, D. Moseev, S.K. Nielsen, M. Salewski, and M. Stejner

Collaborators:E. Westerhof (FOM), O. Schmitz (FZJ), A. Bürger (FZJ), F. Leuterer (IPP), J. Stober (IPP), D. Wagner (IPP), P. Woskov (MIT), and more

19/10/2009Fast ion CTS - present results and ITER plans2 Risø DTU, Technical University of Denmark

Outline• Brief introduction to CTS • Recent experiments with the TEXTOR CTS system • Recent experiments with the ASDEX Upgrade CTS system• The ITER CTS system

– choice of probe frequency– present status of design


• Ions and electrons draw wakes in electron contiuum• On scales larger than the Debye length, λD, the electron

wake looks like an electron hole. Hides the electron.• Ion wakes are dominant cause of microscopic fluctuations.• These collective fluctuations are detected by CTS.• Salpeter parameter set limit for measuring collective

fluctuations:

• Using gyrotrons (mm wave) enables a broad choice ofscattering geometries fulfulling the Salpeter criterion

?

λD

!

1 1Dkδα

λ= >

Microscopic collective fluctuations

E. E. Salpeter, Phys. Rev. 120, 1528, 1960


Collective Thomson scattering resolves the 1D projected velocity distribution along kδ :

kδIncident radiation

Received scattered radiation

ks

kiResolved fluctuations

ReceiverProbe

Collective Thomson scattering geometry

( ) ( ) ( ) ( )1 ˆf u u f dδδ= − ⋅∫ k v v v

kδ = ks - ki


Frq/GHz

Close up

ECE

ECE+CTS

CTS

Extracting CTS signal from raw data

In order to subtract the ECE background the gyrotron is modulated 2 ms on, 2 ms off

• ECE background ~ 20 - 300 eV• Scattered radiation (fast ions) ~ 0.5 - 5 eV


ECE scenarios for mm wave CTSE

CE

Spe

ctra

lPow

er D

ensi

ty(e

V)

Frequency ↑ or Bo ↓

1

1

1 2

2 3

2 3

ITER CTSFTU CTS

JET CTS (1990’s)TEXTOR CTS

AUG CTS


CTS setup at TEXTORGyrotron as probing radiation:110 GHz ~ 2.7 mm, 200 kW, 200 ms

Spatial resolution ~ 5 - 10 cmTemporal resolution ~ 4 ms


CTS setup at TEXTORGyrotron as probing radiation:110 GHz ~ 2.7 mm, 200 kW, 200 ms

Spatial resolution ~ 5 - 10 cmTemporal resolution ~ 4 ms

Steerable mirror

Corrugatedwaveguide

CF 100 flange

In-vesselmirrors

Linear drives

Plasma

Mirrors


TEXTOR overlap scan

TEXTOR top view

S.K. Nielsen et al., Phys. Rev. E (2008), 77 , 016407


TEXTOR topview

1

2

3

4

5

6

7 89

10

11

12

13

14

1516

R0 = 1.75

RT = 1.6

Neutral beam injector 1

Neutral beam injector 2CTS port

Ion cyclotron resonance heating antenna

HCNinterferometer

Electron cyclotron emission (ECE)

IpBT

Co-NBI

Counter-NBI


Co- and counter NBI

Co-

NB

I

Cou

nter

-NB

I

R = 1.87 m ∠ (kδ, B) = 123°

B

vcts

123 °

Ip

Scatteringvolume

Plasma edge

Magneticcentre


Co- and counter NBI

Co-

NB

I

Cou

nter

-NB

I

slices


Resonant magnetic perturbations (RMP) and fast ion losses Aim: Study effect on fast ion confinement during high edge pump out due to resonant magnetic perturbations. Unique possibility to study this at TEXTOR with the presence of the DED and CTS

Measurement volumes

Measure fast ion distribution

• at different radial positions

• at different resolved anglesStudy NBI slowing downtime in non-RMP and RMP phases


CTS at ASDEX Upgrade

• Dual freq. Gyrotron (140 & 105 GHz)• For CTS: fprobe = 105 GHz @ 400 kW CW (10s)• Spatial resolution ~ 2 - 10 cm• Temporal resolution ~ 4 ms

11

1

2

2

22ΩeΩe

F. Meo et al, RSI 79, 10E501 (2008)

ECRH antennae


First results from AUG

• Effect of on and off axis beams in the center of the plasma

• Comparison of one beam with two beams having two different energies– Comparison to TRANSP/NUBEAM


Set up for on-off axis NBI experiment

ComparisonS3 + S8: on-axisS3 + S6: off-axis


Set up for on-off axis NBI experiment

ComparisonS3 + S8: on-axisS3 + S6: off-axis

Frequency up-shift due to the fast ion flow direction is expected from ωδ ≈ vion · kδ.


Comparison: On-axis vs. Off-axis beams

Preliminary findings• Effect marginal!• Agrees with results of lack of

off-axis current– J. Hobirk et al, 30th EPS

Conference on Contr. Fusion and Plasma Phys., St. Petersburg, 7-11 July 2003 ECA Vol. 27A, O-4.1B

• Concurs with theory ofenhanced fast ion transport due to enhanced turbulence(NBI power threshold)

– S. Günter et al, Nucl. Fusion 47, 920 (2007).

• Future experiments includeestablishing NBI power threshold for this enhancedfast ion transport

-3 -2 -1 0 1 2 3 4x 10

6

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2 x 1012

u [m/s]

f [s/

m4 ]

24088: S3+S624089: S3+S8 Off-axis

On-axis

F. Meo et al, submitted to JOP (LAPD invited)


On-axis NBI beams at different energies

• On-axis beams at twodifferent energies

• Comparison to Monte-Carlo/ transport codessimulations

• Change in distribution shape

-2 0 2x 106

0

1

2

u [m/s]

g(u)

[1e1

2 s/

m4 ]

TRANSPNUBEAM

S8 (93 keV)S3 (60 keV) + S8 (93 keV)

ρscat = 0.0 ∠(kδ, B) ≈ 120

°

M. Salewski et al, submitted to Nuclear Fusion, 2009

Bulk

Simulations by Tardini (IPP)


ITER measuring requirements for fast ions

m-3

m-3


Feasibility of a CTS diagnostic for ITER• Four options for probe frequencies. Possibilities influenced by:

– Availability of sources – Ion information in scattered radiation– Access to - and radiation from plasma

Source, ECEOpticallypumped FIR

In upper tail ofECE spec.

3 THz

Source, Small scattering angle

CO2 laserFar above ECE28 THz

ECEGyrotronO-mode, ωc < ωi < 2ωc

170 GHz

Refraction, ECEGyrotronX-mode, ωi < ωc

60 GHz

Main concernLikely sourceRelation to ECE spec.

Probefrequency

H. Bindslev, F. Meo and S.B. Korsholm, ITER Fast Ion Collective Thomson Scattering, Feasibility and Conceptual design (2003) http//cts.risoe.dkH. Bindslev et al, RSI (2004)


ECE scenarios for CTSE

CE

Spe

ctra

lPow

er D

ensi

ty(e

V)

Frequency ↑ or Bo ↓

1

1

1 2

2 3

2 3

ITER CTS 60 GHzFTU CTS

ITER CTS 170 GHzITER CTS FIR & CO2


Limits on scattering angle

0.4°4°50°No limitθmax

28 THz3 THz170 GHz60 GHzνi

Upper limit on scattering angle, θ :

Salpeter criterion restricts the scattering geometry:

19/10/2009Fast ion CTS - present results and ITER plans24 Risø DTU, Technical University of DenmarkSignificant multi year development of source.

Significant multi year development of source.

N/A.Essentially ready.Readiness of the technology

Uncertainty in source performance, and stray-light handling.

Uncertainty in ECE, in detector noise and in source performance.

Reliable, except for performance of specularly reflecting surface.

Reliable.Certainty in performance estimation

Very sensitive.Sensitive.Moderately sensitive.Robust.Robustness to mechanical disturbance and misalignment

Robust.Robust.Robust due to low refraction. Some trouble with receiver beam reflector. Requires steering.

Robust due to wide beam patterns orthogonal to the beam plane.No steering required.

Robustness to plasma variations

No relevant Te limit.No relevant ne limit.

Te < 30 keV (2.7 THz)Te < 35 keV (3.5 THz)No relevant ne limit.

Te limit N/A.No relevant ne limit.

ne < 1.3×1020m-3 for Te < 25 keVne < 1.0×1020m-3 for Te < 35 keV

Operational ranges

500 cm50 cm5 cm20 cmSpatial resolution

Potentially good resolution of the perpendicular velocity distribution.L ≈ 4×Ei/100J

Potentially good resolution of parallel and perpendicular distributions across profile.L ≈ 4×Ei/6J

Poor resolution of perpendicular velocity distribution in one radial location. No resolution of parallel distribution.L < 1×Pi/2MW

Very good resolution of parallel and perpendicular velocity distributions across profile.L > 10×Pi/1MW

Resolving power

28 THz2.7-3.5 THz170 GHz55-60 GHz


Capabilities of the ITER CTS diagnosticBased on a physics feasibility study of 2003 the optimal solution would be

a system:

• Probe is sub-harmonic: 60 GHz (1 MW gyrotron)• Injection near radial to minimize refraction• Consisting of two independent receiver and probe systems – measuring

dynamics of ions ║ and ⊥ to B• Beam shape optimization to ensure overlap• Meets ITER measurement requirements for fusion alphas

– 100 ms – a/10 ~ 20 cm– 0.1 - 3.5 MeV– >16 velocity bins (8 on either side of 0 m/s)

• no movable parts and based on present day technology


Fast ion LFS system – enabled

ki ks

kδ

B

θki ks

kδ

B

θki ks

kδ

B

θ

Port plug #12

The LFS system resolves the perpendicular ion velocity component

Final approval by the ITER Council on June 17th 2009

F. Meo et al, RSI (2004)


Receiver

ProbeB

ks

ki

kδ

θ

Receiver beam

Probe beam

Port plug #12

Fast ion HFS system – not enabledThe HFS system

• resolves the parallel ion velocity component

• provides the toroidal bulk ion rotation


Diagnostic capability and aux heating - NBI

Alpha particle measurements should not be much affected by NBI

Location R=6.35 m, Z=0.55 m, ITER Scenario 2

Location R=5.94 m, Z=0.58 m,ITER Scenario 4

Worst case: resolving the component parallel to B by the HFS-FS CTS receiver

Beam ion distribution functions from ASCOT

Part of EFDA Task (2007/08): TW6-TPDS-DIADEV, Assessment of effects of RF-and NBI-generated fast ions on the measurement capability of diagnostics


In the case of ICRH there could be some interference, but only in the perpendicular direction and in limited areas of space.

R = 6.4 m, Z = 0.68 m Resolving the dynamics perpendicular to B by

the LFS CTS system

R = 5.9 m, Z = 0.55 m Resolving the dynamics parallel

to B by the HFS CTS system

Diagnostic capability and aux heating - ICRH

Worst case: on-axis ICRH at 53 MHz and 20 MW generating fast tritons

ITER Scenario 2ICRH ion distribution functions from PION

Part of EFDA Task (2007/08): TW6-TPDS-DIADEV, Assessment of effects of RF-and NBI-generated fast ions on the measurement capability of diagnostics

M. Salewski et al, Nucl. Fusion 49, 025006 (2009).


Design of the ITER CTS systems

CTS antennae on the low and high field sides (LFS and HFS).


LFS mirror design – 1 mirror solution

CTS LFS receiver beams

CTS LFS receiver mirror

CTS LFS probe beam

Position of CTS LFS receiver horns


ITER CTS HFS mock-up Mark III – 4-mirror receiver

Design drawing of 2007

F. Leipold et al, submitted to RSI (2009)


Modeling of first mirrors for CTS

Beam propagation

Neutron and photonheating

Temperaturedistribution (FEM)

Model deformation (FEM)M. Salewski, RSI 79, 10E729 (2008)


Some key R&D tasks towards the ITER CTS• Design of mirrors

– material, thickness, shape, cooling • Design of in-vessel horns

– shaping of horns defines beam pattern in the plasma• High power transmission lines for probing gyrotron radiation

– propagating through the fundamental resonance– develop and test solution for transmission of a sub-harmonic probe

beam in collaboration with ENEA at FTU• Development of 60 GHz notch filters for the CTS receivers• Calibration sources and methods (contact to US ITER ECE group)


Summary• Fast ion CTS results routinely obtained at TEXTOR• Fast ion CTS at ASDEX Upgrade – physics exploitation has

begun• Design for a 60 GHz fast ion CTS diagnostic for ITER delivered

– LFS front end enabled as part of ITER baseline design diagnostics as of June 17th 2009

cts.risoe.dk


28 THz – CO2 laser for ITER CTS (I)

1238Resolved velocity bins either side of 0

a/6a/3.8a/2.5a/0.6Relative resolution assuming vertical beam line

0.5 m0.8 m1.2 m5 mLength of scattering volume

0.5°0.5°0.5°0.4°Scattering angle

1.3 mm2 mm3 mm10 mmGaussian beam widths

Acceptable resolution in velocity and space cannot be achieved simultaneously with vertical beam


28 THz – CO2 laser for ITER CTS (II)

1m

Source specifications: values in () required to perform as 60 GHz system

• Frequency ~ 28 THz

• Line width and stability ≤ 300 MHz

• Rep. rate = 10 Hz (25 Hz)

• Pulse length ≥ 1 ms (6 ms)

• Pulse power ≥ 100 MW

• Pulse energy ≥ 100 joule (600 joule)

Resolution: a/4

Alternative solution:

Vertical viewingsystem

Scattering volume 5m long in the horizontalplane


The resolving power L• The resolving power L, is a measure of the information of the fast ion

velocity distribution, independent on the chosen number of nodes• Unitless by normalizing with the target accuracy Δ• L2 is approximately the number of nodes resolved with the target accuracy

(provided uncertainties at all nodes are independent)

• 16 nodes ⇒ L > 4 ⇒

60 GHz HFS-FS:

60 GHz LFS-FS:

H. Bindslev, F. Meo and S.B. Korsholm, ITER Fast Ion Collective Thomson Scattering, Feasibility and Conceptual design (2003) http//cts.risoe.dk

fast ion measurements by collective thomson...

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