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Synthetic diagnostic for interpreting the ECE spectrum in LHW-heated plasmas on EAST

Y. Liu1, T. F. Zhou1, A. Ti1, H. L. Zhao1 and L. Figini2

1Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China �2Istituto di Fisica del Plasma, CNR, 20125 Milano, Italy �

2nd IAEA Technical Meeting on Fusion Data Processing, Validation and Analysis 5/30-6/2, 2017 MIT

OUTLINE

!  ECE diagnostic on EAST

!  Motivation of the synthetic diagnostic

!  Preliminary results & future plans

2/20





3/20


Underlying physics of ECE diagnostic

! When the plasma is optically thick, the ECE radiation intensity is the blackbody intensity:

! Electron Cyclotron emission (ECE) at a series of discrete harmonic frequencies：

ECE spectrum " Te profile

! B decreases as 1/R

ECE spectrum Te profile

4/20


Measurement techniques

Advantages: • Wide frequency coverage • Easy to calibrate Disadvantages: • Poor spectral and temporal resolution �

Advantages: • High spectral and temporal resolution Disadvantages: • Limited frequency coverage�

Michelson interferometer Martin-Puplett interferometer

Heterodyne radiometer

5/20

fECE fIF fc Mixer BPF Detector Voltage


Overview of ECE diagnostic on EAST! Quasi-optical antenna: Rotatable ellipsoidal mirror for facilitating on-line calibration ! Transmission line: ~ 45 meters corrugated WG, Double wedged window, Polarizer (X-

mode), Notch filter ! Different measurement systems, with independent in-situ absolute intensity calibration

Heterodyne radiometer Michelson

interferometer

ECE diagnostic room

6/20


30mm

50mm

FWHM

1/e^2

QO antenna for EAST ECE diagnosticCalculated beam size (B0=2.3T)

Measured beam size 7/20


Radiometer systems

8-channel (2015)

From EAST Torus HallTo Michelson

8-channel (2015) 32-channel (2014)+ 8-channel (2015)

! Frequency coverage: 97-168 GHz

! Spectral resolution: 0.2/0.5 GHz

! Temporal resolution: 2.5 us

8/20


Michelson interferometer

Air bearing

Detector

Optical parts

! Frequency coverage: 80-350 GHz ! Spectral resolution: 2.8 GHz ! Temporal resolution: 30 ms

Martin-Puplett layout

9/20


In-situ absolute intensity calibration Calibration results for Michelson interferometer:

Interferogram Spectra

EAST vacuum

Lab

Chopper

Coherent average (Ch05,600oC) Sensitivity (Ch05)

b.g.

Hot source

Calibration results for heterodyne radiometer:

10/20


Te profiles & fluctuation

@1.8 T

@2.47 T

Fishbone instability

Sawtooth instability

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12/20


LHW is of highest priority on EAST

NBI-1

NBI-2

LHW-1

LHW-2

ICRH-1

ICRH-2

ECRH-1

2012: 10MW 2014: 26MW 2016: 26+8MW

! LHW 4+6 MW (2.45/4.6 GHz)

! ICRH 6+6 MW (25-75 MHz)

! NBI 4+4 MW (co/counter, 80 kV)

! ECRH 4 MW (140 GHz)

LHW is of highest CD efficiency & robustness on EAST!

To interpret the ECE data with non-Maxwellian EVD, and reveal information of supra-thermal electrons driven by LHW

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The SPECE simulation code ! Developed by EURATOM-ENEA-CNR Association (Italy) as a support tool for

the Oblique ECE diagnostic at JET ! Originated by the beam-tracing code GRAY (ECH&CD)

D. Farina, FST 52 (2007) 154 ! Main features:

!  Equation of transfer solved in general tokamak equilibrium !  Arbitrary line of sight !  Wave propagation: geometric optics approximation, cold plasma dispersion relation !  EC emission: relativistic description for Maxwellian or multi-Maxwellian distribution

functions !  Detailed description of real ECE diagnostic configuration:

antenna polarization, finite beam-width, wall effects !  Quantifies also ECE localization and spatial resolution

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SPECE: input data

! Magnetic equilibrium (G EQDSK) !  EFIT

! Electron temperature profile !  Thomson Scattering/ECE

! Electron density profile !  Reflectometry

! ECE line of sight

! Wall effects

TS

Refl. ECE LOS

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Simulated ECE spectrum (Ohmic plasma)

I+

I-

r, p (reflectivity, scrambling)

e-τ

Multiple reflections between parallel walls model using empirical coefficients r, p Costley et al., PRL (1974)

17/20


Fast electrons model for LH Simplified model: superposition of Maxwellians drifting along B Brusati et al., NF 34 (1994), 23

€

f ψ, ! u ( ) = 1−η ψ( )( ) ⋅ fM ,Tb

! u ( ) +η ψ( ) ⋅ fM ,Ttail

! u − ! u 0,i( )i=1

N

∑ , η ψ( ) = η0 ⋅ exp −ψ −ψ0( )2

2 ⋅ Δψ 2

⎡

⎣ ⎢ ⎢

⎤

⎦ ⎥ ⎥

18/20


Simulated ECE spectrum (LHW plasma)

€

umax =pmc

= 0.4

Ttail (keV ) = 25η0 = 0.001ψ0 = 0.4Δψ = 0.3

€

umax =pmc

= 0.4

Ttail (keV ) = 25η0 = 0.001ψ0 = 0.3Δψ = 0.2

!  Poor calibration for the low frequency range? !  Inappropriate description of the high-energy tail?

19/20

!  Summary !  Complete set of ECE diagnostic established on EAST !  Synthetic ECE diagnostic with SPECE started

!  Future plans !  To benchmark with GENRAY !  To use CQL3D/GENRAY to simulate EVD

Summary & future plans

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