Recent progress on Thomson scattering diagnostic on HL-2A tokamak

Abstract

Some new progress has been made to develop the multi-point Thomson scattering (TS) diagnostic for the HL-2A tokamak physics experiments. Hardware of silicon avalanche photodiode detector electronics, motorized stages to control the laser beam for beam alignment, 3 modules of fast digitizers with more than 100 channels to record the time evolution of the TS pulses at 2.5 GS/s with 12-bit resolution, and 15 polychromators for 15-point measurements of core plasma electron temperature. The data processing code is further adjusted to manage the digitized raw data. The TS intensity is obtained by direct summing method and by Gaussian-function fitting, respectively, and then different value of electron temperature is derived by the technique of weighted least-squares regression. As to the latter, the electrical noise and perturbations of the TS signal is significantly reduced, the resulting value of electron temperature has a better quality than that of the former. New processing code is in development.