Doppler Reflectometer System for Measuring Rotation Velocity of Fluctuation in GAMMA 10

Abstract

Doppler reflectometry is currently used as a powerful technique to measure the perpendicular (to the magnetic field) velocity of density fluctuation, the radial electric field, and the perpendicular wave number spectrum in many fusion plasma devices. In GAMMA 10 a Doppler reflectometer has recently been installed to measure perpendicular rotation velocity of density fluctuation in the cylindrical plasma. The Doppler reflectometer has an antenna system with a launching/receiving scalar feed antenna and focusing mirrors. By rotating one of the mirrors the tilt angle of the incident microwave can be controlled against the normal of cutoff layers. A frequency synthesizer is used in the range 11.5 -18 GHz as the stable microwave source of X-mode probing beam for GAMMA 10 plasma having typical peak density ∼ 2 × 10 18 m −3 . The first preliminary results of Doppler shifted spectra and radial profiles of the perpendicular velocity of density fluctuations are presented for ICRF start-up plasma with additional ECH. The rotation of fluctuations during additional ECH period is found to become opposite direction comparing to the case of ICRF heating alone.

Application of Dual Frequency Comb Method as an Approach to Improve the Performance of Multi-Frequency Simultaneous Radiation Doppler Radar for High Temperature Plasma Diagnostics

“…Since electromagnetic waves in the millimeter-wave range can be used in relation to the electron plasma frequency and the electron cyclotron frequency range, the system is expected to be used as a stable and robust measurement method, and is also expected to be used in future nuclear burning fusion reactors. In fusion plasma research, this Doppler radar is called a Doppler reflectometer or a Doppler back-scattering and has been applied to various experimental devices around the world, such as helical/stellarators (Wendelstein 7-AS [1,2], 7-X [3], TJ-II [4], LHD [5][6][7][8]), tokamaks (Tuman-3M [9], ASDEX Upgrade [10][11][12][13], Tore Supra [14,15], DIII-D [16,17], JT-60U [18], MAST [19], JET [20], HL-2A [21], TCV [22], EAST [23][24][25]), and linear machines (C-2 FRC [26], GAMMA-10 [27]). In particular, in recent years, systems capable of simultaneous multi-frequency observation have been developed with the aim of understanding the instantaneous spatial structure of turbulence [6][7][8]13,17,[21][22][23][24][25].…”