Optical tomography diagnostic for study of neutral plasma component in the gas dynamic trap

Abstract

The optical diagnostic observing D-𝛼 line emission along multiple chords in the boundary region close to the plasma absorber, is recently installed at the gas dynamic trap. The implemented pattern of viewing lines is suitable for a tomographic reconstruction of local emissivity profiles, although steps towards increasing the channel count and extending of angular plasma coverage must be taken. The optical registration system of a modular design uses avalanche photodiodes with wideband amplifiers for a large signal dynamic range and the effective time resolution of 1𝜇𝑠. The iterative backward projection technique based on the maximum likelihood principle, demonstrates an acceptable computation accuracy. Images of plasma evolution in the cross section were obtained. Tools for the correlation analysis were also developed and first results of study of the plasma turbulence are presented.