EBW Emission & Coupling Physics Important for T e (R) Diagnostic Development & EBWCD System Design

1 XP514: EBW Emission & Coupling - Taylor NSTX Results Review 12/13/05

XP514: Thermal Electron Bernstein Wave XP514: Thermal Electron Bernstein Wave

Emission & Coupling on NSTXEmission & Coupling on NSTX

G. TaylorG. Taylor11, J.B. Caughman, J.B. Caughman22, S.J. Diem, S.J. Diem11, , P.C. EfthimionP.C. Efthimion11, B.P. LeBlanc, B.P. LeBlanc11, R.W. Harvey, R.W. Harvey33,,

J. PreinhaelterJ. Preinhaelter44, J.B. Wilgen, J.B. Wilgen22

1)1) Princeton Plasma Physics LaboratoryPrinceton Plasma Physics Laboratory2) Oak Ridge National Laboratory2) Oak Ridge National Laboratory

3) CompX3) CompX4) Czech Institute of Plasma Physics4) Czech Institute of Plasma Physics

NSTX Results ReviewNSTX Results ReviewDecember 13, 2005December 13, 2005


EBW Emission & Coupling Physics Important forEBW Emission & Coupling Physics Important forTTee(R) Diagnostic Development & EBWCD System Design(R) Diagnostic Development & EBWCD System Design

M. CarterORNL

AORSA-1DNSTX = 40%Bt(0) = 3.5 kGf = 28 GHz

• Need resilient EBW coupling forNeed resilient EBW coupling for EBWCD & TEBWCD & Tee(R) diagnostic(R) diagnostic

• XP514 studied oblique O-mode XP514 studied oblique O-mode 2nd harmonic EBW coupling2nd harmonic EBW coupling

UHR

SXEBW

O

N

R

€

T ( N⊥,N // ) = exp −πkoLn (Y / 2) 2(1+Y )( N //, opt − N // )2 + N⊥

2[ ]{ }

Where: Y = ce/


Dual-Channel 20-40 GHz Radiometer & Quad-Ridged Horn Dual-Channel 20-40 GHz Radiometer & Quad-Ridged Horn Provides Orthogonal Polarization MeasurementsProvides Orthogonal Polarization Measurements

20-40 GHzRadiometer 1

20-40 GHzQuad Ridged

Antenna

Lens

VacuumWindow

EBWEmission

Plasma

20-40 GHzRadiometer 2

Rφ

Z

-Voltage Controlled Local Oscillator

-Two WayPowerSplitter

Arbitrary WaveformGenerator

• Measure TMeasure Tee(R,t) via thermal EBW emission(R,t) via thermal EBW emission

• Analyze polarization of thermal EBW emissionAnalyze polarization of thermal EBW emission• Demonstrate > 80% coupling of thermal EBWs at ~ 28 GHzDemonstrate > 80% coupling of thermal EBWs at ~ 28 GHz

Experiment Goals:Experiment Goals:

• Antenna could be manually steered with some Antenna could be manually steered with some difficultydifficulty


Obtained Good EBW Emission, TObtained Good EBW Emission, Tee, n, nee & EFIT Data to & EFIT Data to

Compare to Modeling, Despite Locked ModesCompare to Modeling, Despite Locked Modes

• NBI-heated H-mode target plasma; measured EBW NBI-heated H-mode target plasma; measured EBW emission between 24 & 32 GHz during dedicated half-dayemission between 24 & 32 GHz during dedicated half-day

• Acquired data at IAcquired data at Ipp = 0.8 & 0.9 MA, early termination at = 0.8 & 0.9 MA, early termination at

IIpp = 1 MA due to locked mode = 1 MA due to locked mode

• Ran frequency scan at IRan frequency scan at Ipp = 0.8 MA, but conditioning/fueling = 0.8 MA, but conditioning/fueling

changed & developed locked modes during scanchanged & developed locked modes during scan

• Emission bursting events, particularly immediately prior to Emission bursting events, particularly immediately prior to locked modeslocked modes

• Compared experimental results to full wave mode Compared experimental results to full wave mode conversion & 3-D ray tracing codes conversion & 3-D ray tracing codes


0.2

0.3

0.4

0.5

0.6

24

Frequency (GHz)

26 28 30 32

Trad (keV)0 0.75Trad (keV)00.3

24

Frequency (GHz)

26 28 30 32

Measured Simulated

Time (s)Shot 117970

Bt(0) = 4.5 kG

Evolution of Measured 24-32 GHz EBW Emission from Evolution of Measured 24-32 GHz EBW Emission from H-Mode had TH-Mode had Tradrad ~ 2-4 Times Smaller than Simulation ~ 2-4 Times Smaller than Simulation

Simulation used Zeff = 1.36 at UHR


Frequency = 25 GHzShot 117970 @ 0.298s

Z(m)

1.0

-1.0

0

0.5 1.0 1.5R(m)

0.05

0Z(m)

R(m)

-0.05

-0.11.0 1.2 1.4

EBW Ray Tracing

2fce Emission

Te

R(m)1.0 1.2 1.4 1.6

0

1.0

Te(keV)

fUHR

2fce

3fceFreq. (GHz)

25 GHz

0

20

40

60

AxisLast ClosedFlux Surface

fUHR

2fce

3fce Emission

• Radial access betweenRadial access between 2f2fcece & 3f & 3fcece sensitive to sensitive to

EBW nEBW n//// due to EC due to EC

resonance Dopplerresonance Doppler broadeningbroadeningEBW Ray Tracing

Measured TMeasured Tradrad at 25 GHz from 2f at 25 GHz from 2fce ce On-Axis, On-Axis, & 3f& 3fce ce Off-axis; Harmonic Mix Sensitive to EBW nOff-axis; Harmonic Mix Sensitive to EBW n////


Collisional Loss at Upper Hybrid Resonance (UHR) Collisional Loss at Upper Hybrid Resonance (UHR) May Explain Low Measured EBW TMay Explain Low Measured EBW Tradrad

• Measured EBW couplingMeasured EBW coupling efficiency (Tefficiency (Tradrad/T/Tee) ~ 20%) ~ 20%

• Emission polarizationEmission polarization agrees with simulationagrees with simulation

• TTee ~ 10-30 eV near UHR ~ 10-30 eV near UHR

• Collisional losses can be Collisional losses can be significant for Tsignificant for Te e < 30 eV:< 30 eV:

- EBW conversion- EBW conversion efficiency sensitive toefficiency sensitive to ZZeffeff at low T at low Tee

Measured Trad

Simulated Trad with no collisionsSimulated Trad with Zeff = 3 at UHRSimulated Trad with Zeff = 5 at UHR

Shot = 117970Frequency = 25 GHz

MeasuredEmission

Polarization(Epara/Eperp)

Trad(keV)

PolarizationFrom

Simulation

1000

Time (s)


XP514 SummaryXP514 Summary

• Completed first measurements of 2Completed first measurements of 2ndnd harmonic EBW harmonic EBW coupling to O-mode from H-mode NSTX plasmas coupling to O-mode from H-mode NSTX plasmas

• Coupling efficiency only ~ 20%:Coupling efficiency only ~ 20%:

- modeling indicates low T- modeling indicates low Tee & Z & Zeff eff ~ 3 at UHR~ 3 at UHR

can cause significant EBW collision loss at UHRcan cause significant EBW collision loss at UHR

- ~ 80% fundamental EBW coupling from L-mode - ~ 80% fundamental EBW coupling from L-mode NSTX plasmas last year; higher TNSTX plasmas last year; higher Tee at UHR at UHR

- still analyzing EBW emission data obtained during- still analyzing EBW emission data obtained during other experiments during 2005 run other experiments during 2005 run

• Detailed 8-40 GHz thermal EBW emission coupling studyDetailed 8-40 GHz thermal EBW emission coupling study on NSTX in 2006-7 with two remotely-steered antennason NSTX in 2006-7 with two remotely-steered antennas

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EBW Emission & Coupling Physics Important for T e (R) Diagnostic Development & EBWCD System Design