Doppler Backscattering (DBS) System on EAST

1. Doppler Backscattering (DBS) System on EAST A.D. Liu, C.X. Yu, H. Li, C. Zhou, X.H. Zhang, J.Q. Hu, W.D. Liu Dept. of Modern Physics, USTC E.J. Doyle, W.A. Peebles, C. Wannberg, X. Nguyen, G. Wang Dept. of Physics and Astronomy, UCLA July 11, 2012

2. Outline • 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

3. Purpose 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;

4. Schematic Diagram frequency modulation technique 55,57.5,60,62.5,67.5,70,72.5,75GHz 8-channel output RF LO used to decrease both the frequency of LO and RF

5. Schematic Diagram of the DBS System RF LO RSI J.C. Hillesheim 2009 8-channel I&Q

6. Microwave Source/Receiver System • The microwave circuit is already been constructed and tested on platform;

7. Microwave Source/Receiver System Test • The spectra of three LO signals and IQ mixer output; 67.5GHz 75GHz 55GHz

8. Ray Tracing Performed for EAST H-mode L-mode • 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

9. Internal 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;

10. Current DBS system on EAST fixed flat mirror quartz oscillator transmit/receive antenna quadrupler isolator amplifier directional coupler Synthesizer 2-20GHz mixer rotating parabolic mirror IQ detector DAQ features: # monostatic, corrugated antenna # X-mode only, Q&V bands

11. Current 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 Q-band over - mode waveguide V-band Doppler ref.

12. 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; eiφ

13. 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;

14. 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;

15. 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; kθ=6cm-1 appear disappear

16. Summary • 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

17. THANKS!