Development of a 105 GHz fast ion collective Thomson scattering diagnostic on HL-2A tokamak

Abstract

Collective Thomson Scattering (CTS) diagnostic technique has great potential in measuring velocity distribution of fast ions in magnetically confined fusion devices. Here we present design and development of a 105 GHz fast ion CTS system on HL-2A tokamak. The gyrotron with high power transmission/antenna is used to generate a probe beam. To better focus the scattering beam and effectively avoid the stray contamination, a W-band Cassegrain antenna is utilized to receive the scattering beam from the central chord. The scattering signal is estimated at 10–30 eV and the frequency broadening is less than 2 GHz for typical HL-2A plasmas. To pick out the weak signals, a multi-channel receiver system with working frequency of 103–107 GHz is developed. The steerable direction of probe beam enables that the scattering volume can move from core to edge, with which the spatial resolution range varies from 70 mm at low field side to 260 mm at high field side.

ITER collective Thomson scattering—Preparing to diagnose fusion-born alpha particles (invited)

“…Collective Thomson scattering diagnostic systems for measurements of both thermal ions and fast ions have been installed on several current and past tokamaks and stellarators. These include in chronological order of installation: TCA 4 , W7-AS 5 , JET 6,7 , TEXTOR [8][9][10][11] , ASDEX Upgrade [12][13][14][15] , FTU 16 , LHD 17,18 , W7-X 19 , and recently also HL-2A 20 . With the exception of the D 2 O-laser probe at TCA 4 , all the ion CTS diagnostics have been implemented using gyrotronstypically in the frequency range from 77 GHz to 140 GHz, which matches the low-intensity ECE frequency range between the fundamental and the second harmonic electron cyclotron resonances.…”