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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
19/10/2009Fast ion CTS - present results and ITER plans3 Risø DTU, Technical University of Denmark
• 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
19/10/2009Fast ion CTS - present results and ITER plans4 Risø DTU, Technical University of Denmark
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
19/10/2009Fast ion CTS - present results and ITER plans5 Risø DTU, Technical University of Denmark
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
19/10/2009Fast ion CTS - present results and ITER plans6 Risø DTU, Technical University of Denmark
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
19/10/2009Fast ion CTS - present results and ITER plans7 Risø DTU, Technical University of Denmark
CTS setup at TEXTORGyrotron as probing radiation:110 GHz ~ 2.7 mm, 200 kW, 200 ms
Spatial resolution ~ 5 - 10 cmTemporal resolution ~ 4 ms
19/10/2009Fast ion CTS - present results and ITER plans8 Risø DTU, Technical University of Denmark
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
19/10/2009Fast ion CTS - present results and ITER plans9 Risø DTU, Technical University of Denmark
TEXTOR overlap scan
TEXTOR top view
S.K. Nielsen et al., Phys. Rev. E (2008), 77 , 016407
19/10/2009Fast ion CTS - present results and ITER plans10 Risø DTU, Technical University of Denmark
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
19/10/2009Fast ion CTS - present results and ITER plans11 Risø DTU, Technical University of Denmark
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
19/10/2009Fast ion CTS - present results and ITER plans12 Risø DTU, Technical University of Denmark
Co- and counter NBI
Co-
NB
I
Cou
nter
-NB
I
slices
19/10/2009Fast ion CTS - present results and ITER plans13 Risø DTU, Technical University of Denmark
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
19/10/2009Fast ion CTS - present results and ITER plans14 Risø DTU, Technical University of Denmark
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
19/10/2009Fast ion CTS - present results and ITER plans15 Risø DTU, Technical University of Denmark
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
19/10/2009Fast ion CTS - present results and ITER plans16 Risø DTU, Technical University of Denmark
Set up for on-off axis NBI experiment
ComparisonS3 + S8: on-axisS3 + S6: off-axis
19/10/2009Fast ion CTS - present results and ITER plans17 Risø DTU, Technical University of Denmark
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.
19/10/2009Fast ion CTS - present results and ITER plans18 Risø DTU, Technical University of Denmark
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)
19/10/2009Fast ion CTS - present results and ITER plans19 Risø DTU, Technical University of Denmark
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)
19/10/2009Fast ion CTS - present results and ITER plans20 Risø DTU, Technical University of Denmark
ITER measuring requirements for fast ions
m-3
m-3
19/10/2009Fast ion CTS - present results and ITER plans21 Risø DTU, Technical University of Denmark
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)
19/10/2009Fast ion CTS - present results and ITER plans22 Risø DTU, Technical University of Denmark
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
19/10/2009Fast ion CTS - present results and ITER plans23 Risø DTU, Technical University of Denmark
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
19/10/2009Fast ion CTS - present results and ITER plans25 Risø DTU, Technical University of Denmark
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
19/10/2009Fast ion CTS - present results and ITER plans26 Risø DTU, Technical University of Denmark
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)
19/10/2009Fast ion CTS - present results and ITER plans27 Risø DTU, Technical University of Denmark
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
19/10/2009Fast ion CTS - present results and ITER plans28 Risø DTU, Technical University of Denmark
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
19/10/2009Fast ion CTS - present results and ITER plans29 Risø DTU, Technical University of Denmark
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).
19/10/2009Fast ion CTS - present results and ITER plans30 Risø DTU, Technical University of Denmark
Design of the ITER CTS systems
CTS antennae on the low and high field sides (LFS and HFS).
19/10/2009Fast ion CTS - present results and ITER plans31 Risø DTU, Technical University of Denmark
LFS mirror design – 1 mirror solution
CTS LFS receiver beams
CTS LFS receiver mirror
CTS LFS probe beam
Position of CTS LFS receiver horns
19/10/2009Fast ion CTS - present results and ITER plans32 Risø DTU, Technical University of Denmark
ITER CTS HFS mock-up Mark III – 4-mirror receiver
Design drawing of 2007
F. Leipold et al, submitted to RSI (2009)
19/10/2009Fast ion CTS - present results and ITER plans33 Risø DTU, Technical University of Denmark
Modeling of first mirrors for CTS
Beam propagation
Neutron and photonheating
Temperaturedistribution (FEM)
Model deformation (FEM)M. Salewski, RSI 79, 10E729 (2008)
19/10/2009Fast ion CTS - present results and ITER plans34 Risø DTU, Technical University of Denmark
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)
19/10/2009Fast ion CTS - present results and ITER plans35 Risø DTU, Technical University of Denmark
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
19/10/2009Fast ion CTS - present results and ITER plans36 Risø DTU, Technical University of Denmark
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
19/10/2009Fast ion CTS - present results and ITER plans37 Risø DTU, Technical University of Denmark
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
19/10/2009Fast ion CTS - present results and ITER plans38 Risø DTU, Technical University of Denmark
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