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Doppler Backscattering (DBS) System on EASTDoppler Backscattering (DBS) System on EAST

A.D. Liu, C.X. Yu, H. Li, C. Zhou, X.H. Zhang, J.Q. Hu, W.D. LiuDept. of Modern Physics, USTC

E.J. Doyle, W.A. Peebles, C. Wannberg, X. Nguyen, G. WangDept. of Physics and Astronomy, UCLA

July 11, 2012

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OutlineOutline

• Purpose of the 8-channel DBS System

• Schematic Diagram of the System

• Status of construction and testing of microwave source/receiver system

• Ray-tracing calculations for EAST

• Design for internal optical arrangement on EAST

• Preliminary results of current Q&V band DBS system

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Purpose of the 8-channel DBS SystemPurpose of the 8-channel DBS System

• 8 frequency points from 55-75GHz are chosen; Multipoint measurements of density fluctuation through Doppler back-scattering; This system is designed and constructed by UCLA;

• Measurement of Er and flow velocity;

• Turbulence levels for studies of improved confinement regimes;

• Turbulence characterization for code/model validation studies;

• Spatially resolved measurements of EP and NTM mode activity, especially mode structure;

• Edge and core studies of Zonal flows and GAMs;

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Schematic DiagramSchematic Diagram

55,57.5,60,62.5,67.5,70,72.5,75GHz8-channel output

frequency modulation technique

LO

used to decrease both the frequency of LO and RF

RF

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Schematic Diagram of the DBS SystemSchematic Diagram of the DBS System

RSI J.C. Hillesheim 2009

LORF

8-channel I&Q

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Microwave Source/Receiver SystemMicrowave Source/Receiver System

• The microwave circuit is already been constructed and tested on platform;

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Microwave Source/Receiver System TestMicrowave Source/Receiver System Test

• The spectra of three LO signals and IQ mixer output;

55GHz 67.5GHz 75GHz

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Ray Tracing Performed for EASTRay Tracing Performed for EAST

• Ray tracing calculations for different incident angles in L- and H-mode EAST plasma scenarios;

• Vary location and angle of probe beam launch to determine optimum design location and range of angles

L-mode H-mode

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Internal Optics Arrangement for EASTInternal Optics Arrangement for EAST

• Corrugated waveguide would be used for the low loss and the better quality Gaussian beam;

• Fixed parabolic mirror with moveable flat mirror;

• The detail is under designing;

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Current DBS system on EASTCurrent DBS system on EAST

directionalcoupler

isolator

quadrupler

amplifier

mixer

transmit/receiveantenna

quartz oscillator fixed flat mirror

IQ detector

DAQ

rotating parabolicmirror

Synthesizer2-20GHz

features:# monostatic, corrugated antenna # X-mode only, Q&V bands

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Current DBS system installed on EASTCurrent DBS system installed on EAST

• Before and after the LH transition, the spectra of DBS phase signals are shown, and the Doppler shift increases largely during H-mode;

servo motor

Doppler ref.

over-mode waveguide

Q-band

V-band

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eiφ

Preliminary results of EGAM during ICRF H-mode Preliminary results of EGAM during ICRF H-mode

• The injected ICRF power is about 2MW and type III ELMy H-mode is obtained;

• During the intervals between two adjacent ELMs, modes could be observed on both the spectrum of DBS phase signal and magnetic coils;

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Preliminary results of EGAM during ICRF H-mode Preliminary results of EGAM during ICRF H-mode • Strong coherence between DBS phase

φ and magnetic coil signals at f=38kHz;• The coherence spectra between two

magnetic coils separated π toroidally imply the toroidal symmetry of the mode;

• The spectrum of DBS signal implied the poloidal symmetry of the mode;

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Preliminary results of EGAM during ICRF H-mode Preliminary results of EGAM during ICRF H-mode • The bicoherence of DBS phase signal

φ(t) show the coupling between the mode and broadband high frequency components, similar to the zonal flows;

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Preliminary results of EGAM during ICRF H-mode Preliminary results of EGAM during ICRF H-mode • The bicoherence of DBS phase signal

φ(t) show the coupling between the mode and broadband high frequency components, similar to the zonal flows;

• The phenomena only be observed in the core plasmas under H-mode;

• Not observed on ECE imaging signals at the same radius;

• It may be GAM induced by high energy ions, however, there is no direct measurement of high energy ions on EAST;

• More analyses is in process;

appear

disappear

kθ=6cm-1

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SummarySummary

• The microwave circuit of the 8-channel DBS system has already been constructed and tested in UCLA;

• Conceptual designs for internal optical system was generated and the corrugated waveguide will be used;

• The new 8-channel DBS system will be tested on EAST in next campaign;

• Another separated Q&V band DBS system was installed and tested on EAST for the first time, the features of EGAM were observed during ICRF H-mode;– strong coherence between DBS phase and magnetic coil signal;– n=0 deduced from the magnetic coils– m=0 deduced from spectrum of DBS signal– The bicoherence of the DBS phase signal implied the interaction between the mode

and broad turbulence, similar with zonal flows– appear at the core regime in H-mode

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THANKS!THANKS!