Design of multipulse Thomson scattering diagnostic for SST-1 tokamak.

A multipulse Nd:YAG (Yttrium aluminum garnet) Thomson scattering (TS) system is designed and developed for measuring electron temperature (T(e)) and density (n(e)) profiles of SST-1 tokamak. The system operates at vertical, divertor, and horizontal (midplane) regions of plasma and measures the electron temperature of 20 eV to 1.5 keV and density of 10(18)-10(19) m(-3). Six Nd:YAG lasers synchronized with external control is used to get three different temporal resolutions (30 Hz, 180 Hz, and 1 kHz). The entire system is laboratory tested for the stability of alignment and performance over a distance of 30 m. Different imaging lens assemblies are designed to image the scattered photons from each of the scattering region to an array of optical fibers. A low cost and compact five-channel interference filter polychromator is designed, fabricated, and tested for its image quality and the filter transmission characteristics. Detection system with an avalanche photodiode and required signal conditioning electronics is developed for detecting the scattered photons. A data acquisition and control module operating on PXI bus is developed for the real time data acquisition and system control. A detailed description of design and testing of TS subsystems is presented in this article.