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NSTX Physics Meeting at PPPL, June 1, 2009. OXB-converted E BWs in Tokamaks, Spherical Tokamaks, Stellarators and RFPs. Francesco Volpe Engineering Physics Department University of Wisconsin, Madison. Outline. Motivation Principle of EBWs and Mode Conversions EBWs in - PowerPoint PPT Presentation
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NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 1
OXB-converted OXB-converted EEBWs in BWs in Tokamaks, Spherical Tokamaks, Tokamaks, Spherical Tokamaks,
Stellarators and RFPsStellarators and RFPs
Francesco Volpe
Engineering Physics Department
University of Wisconsin, Madison
NSTX Physics Meeting at PPPL, June 1, 2009
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 2
OutlineOutline
Motivation
Principle of EBWs and Mode Conversions
EBWs in
Summary & Conclusions
This Talk Madison World
Stellarator W7-AS HSX CHS, Heliotron, LHD, WEGA
Sph.Tokamak MAST Pegasus Mini-RT, NSTX
Tokamak TCV DIII-D?
RFP RFX-mod MST
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 3
Motivation for Electron Bernstein WavesMotivation for Electron Bernstein Waves
Several MCF plasmas are too dense or have too low magnetic fieldfor conventional Electron Cyclotron Resonant Heating (ECRH)
EBWs do not suffer from upper density limits
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 4
Electron Bernstein wavesElectron Bernstein waves
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 5
Marine waves are another example of Marine waves are another example of gyrophase organizationgyrophase organization
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 6
OXB-SchemeOXB-Scheme: : special view makes modes degenerate special view makes modes degenerate and not evanescentand not evanescent
p
0
1
z
B
L
Slow X
OL
O-wave cut-off
x
In the real space In the phase space
x
sin2=N2z,opt=Y/(Y+1), Y=c/
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 7
OXB-SchemeOXB-Scheme: : O-X conversionO-X conversion
Merging of O and SX waves
when their cutoffs overlap:
SXOAiry
even
odd
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 8
SX-B mode conversionSX-B mode conversion
Finite Larmor radius
6th order correction to Booker quartic
Deflection from UHR and
Propagation at X>1 (overdense), until
Cyclotron damping
Conversion efficiency can be limited by:
- Collisional damping (if edge cold)
- Back-tunneling SX-FX (if barrier thin)
- Parametric decay (at high power)
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 9
EBW Emission, Heating & CDin the W7-AS Stellarator
(with H.P. Laqua)
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 10
AntennaAntenna
Max Transmission
Min Doppler effects
Pure O-mode detection
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 11
Oblique view makes polarization elliptical. Oblique view makes polarization elliptical. Broadband phase-shifter corrects it.Broadband phase-shifter corrects it.
polarization rotator/4 phase shifter
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 12
Ray tracingRay tracing
/
r/N
/
N/r
D
D
d
d
D
D
d
d
5th order Runge-Kutta
OX: 1) optimization of injection angle,
2) symmetries in narrow evanescent layer
XB: Ridder‘s method to correct N
Full stellarator geometryPoloidal component
Off-midplane launch
Toroidal curvature
Broken axisymmetry
Parallel computing on 16 workstation cluster
D=Det(ij+NiNj-N2ij), =hot diel.tensor
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 13
EBEEBE Spectrum and ProfileSpectrum and Profile
ne from TS and Li-Beam
B from equilibrium code TRANS} mapping f r
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 14
Heat Waves: EB-diagnostic during EB-heatingHeat Waves: EB-diagnostic during EB-heating
EBH
Overlapped thermal spectrum cannot be measured at the same harmonic
Non-thermal peaks fpumpnfLH (n=1,2,...)
Parametric decay
Problem:
EBH 2nd harm. & EBE 1st harm.
Plasma has to be O2-overdense
(at least ne >2.4·1020 m-3,
recently ne 4 ·1020 m-3)
Solution:
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 15
Edge-localized ModesEdge-localized Modes
Cross-correlation with H:
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 16
Due to oblique injection, OXB heating also drives current !Due to oblique injection, OXB heating also drives current !
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 17
Angle is fixed by OXB, but co/ctr-CD can be selected and Angle is fixed by OXB, but co/ctr-CD can be selected and NN|||| adjusted by varying the magnetic configuration adjusted by varying the magnetic configuration
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 18
EBW Emission & Heatingin the MAST Spherical Tokamak
(with V. Shevchenko)
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 19
Emission in a spherical tokamak is “banded” as a Emission in a spherical tokamak is “banded” as a consequence of low aspect ratioconsequence of low aspect ratio
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 20
EBE evidenced fast electrons at sawtooth crashesEBE evidenced fast electrons at sawtooth crashes
D
Soft-X Rays
EBE 60.5GHz
62.5GHZ
63.5GZ
66.5GHz
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 21
2D angular scans of EBW emission indicated optimal 2D angular scans of EBW emission indicated optimal direction for heating at MAST spherical tokamakdirection for heating at MAST spherical tokamak
-7 -6 -5 -40.0
0.2
0.4
0.6
0.8
1.0
f=60.5GHz, = -7deg
BX
O-E
BW
Sig
nal (
a.u.
)
Poloidal angle (deg)
-11 -10 -9 -8 -7 -6 -5
0.0
0.2
0.4
0.6
0.8
1.0f=60.5GHz, = -5.6deg
B
XO
-EB
W S
igna
l (a.
u.)
Toroidal angle (deg)
2.5o FWHM 1.2o FWHM
In spite of non-optimal frequency (60GHz) and alignment issues
Time, sec
60 kJ (~3 MW)
7 kJ (~ 0.25 MW)
250 kW
EC
RH
Po
we
rT
ota
l E
ne
rgy
Emission
Heating
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 22
Btotal
ne
PlasmaO-mode
O-mode
2D angular scans confirmed that emission is anisotropic 2D angular scans confirmed that emission is anisotropic New q-profile diagnostic conceptNew q-profile diagnostic concept
Inclination of conversion contours at various f givesInclination of field line at various radial positions
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 23
3.3585 tonnes
3.3585 tonnes
Self-balanced design spins at 12,000rpm
First measurements carried out. Analysis under way.
Special design allows tilted mirror to spin at 12,000rpm and Special design allows tilted mirror to spin at 12,000rpm and scan EBW emission within the same dischargescan EBW emission within the same discharge
EBE from
plas
ma
to ra
diom
eter
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 24
EBW Heatingin the TCV Tokamak
(with A. Mϋck, L. Curchod, A. Pochelon et al.)
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 25
Angular Scan of EBW injection shows min stray Angular Scan of EBW injection shows min stray (max conversion) close to calculated optimum (max conversion) close to calculated optimum
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 26
EBWH at EBWH at ~0.4resulted in clear, ~0.4resulted in clear, bigger-than-sawtooth Tbigger-than-sawtooth Te e increaseincrease
Te builds over e~50ms
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 27
Modeling of EBW Current Drivein the RFX-mod RFP
(with R. Bilato and A. Köhn)
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 28
Peculiarities of EBWs in RFPsPeculiarities of EBWs in RFPs
1. |B| almost poloidally symmetric.
Any launch is Low Field Side (LFS).
No High Field Side (HFS) schemes, e.g. no SX-B.
2. low B low ce low long vacuum wavelength λ cutoffs and resonances “close” to each other tunneling
3. ne fluctuations cutoff corrugated and moves.
B fluctuations optimal direction, Nz,opt
2 = ce/(ce+), fluctuates
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 29
28GHz (228GHz (2ndnd harmonic) considered for EBWCD at field harmonic) considered for EBWCD at field reversal. Expected 58% conversion efficiency reversal. Expected 58% conversion efficiency
Limiting factors to higher efficiency:curvature mismatch (included)fluctuations (not included)
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 30
Multiple reflections by graphite wall re-inject some power Multiple reflections by graphite wall re-inject some power and increase overall OXB efficiency to 67%and increase overall OXB efficiency to 67%
R or FX cutoffUH resonance
P or O cutoffL or SX cutoff
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 31
Summary and ConclusionsSummary and Conclusions
• Stellarators need EBWs
- overdense
+ Mode-converted EBWs benefit from Stellarator environment
- steep gradients, external control of configuration, tolerable ne and B fluctuations
= A marriage!
• EBW heating, emission and CD all proved in W7-AS stellarator
• In spite of 60GHz being too high, EBW heating succeded also in MAST,
- after scenario optimization (steep gradients)
- and guidance from EBW emission (optimal direction).
• “Spinning mirror” provided angular scans of OXB conversion efficiency every 10ms possible q-profile diagnostic.
• EBW heating also proved in TCV tokamak
• EBW CD at edge of RFX-mod RFP plasma might trigger tranport barrier
NSTX Phys. Meeting, June 1, 2009 “OXB-converted EBWs” (F. Volpe) 32
Long-term (power-plant and CTF) applications of EBWsLong-term (power-plant and CTF) applications of EBWs
Stellarators: compensation for undesired bootstrap current at high
Sph.Tokamaks: Non-inductive start-up and growth of a target for NBI.
Current profile tailoring.
Tokamaks: Te diagnosis of ITER divertor region? Not overdense, but Upper Hybrid resonant layer (thus, EBWs) exists.
RFPs: Improved confinement by suppressing MHD and triggering transport barriers at reversal layer.