Measurements of Atomic Hydrogen-Density Profiles in the RFC-XX-M Machine Using Laser Fluorescence Spectroscopy at the Hα Transition

Abstract

To assist in the study of the power balance in a linear confinement machine, atomic hydrogen-density profiles in plasmas of the RFC-XX-M device were measured using laser fluorescence spectroscopy tuned to the Balmer alpha line. Measured profiles showed marked decreases of neutral densities in the centre of the plasma, which are explained by charge-exchange and electron ionization pumping by the plasma. It is important to note that the neutrals are well burned out in the central cell, N_l/N_e \lesssim0.01. Further, charge-exchange losses are quantitatively evaluated and discussed from the neutral-density profiles and parameters of the plasma.