Spectroscopic study of neutral species in a planar-coil inductive discharge in hydrogen

Abstract

This contribution reports on an experimental study of characteristics of the neutrals in a single element of a matrix source of negative hydrogen ions. The investigations are carried out in hydrogen discharges maintained at a frequency of 27 MHz, applied power varied in the limits P = (50–150) W and pressure in the range p = (90–160) mTorr. An optical emission spectroscopy diagnostics, based on analysis of the spectral line profile and the intensity distribution of the Fulcher-α molecular band, is used. The profile of the atomic line reveals the existence of thermal as well as of non-thermal (fast) hydrogen atoms in the discharge. For processing the experimental data a line shape model, accounting for details of the plasma kinetics and the fine structure of the line, is used. The temperature of the atoms in the excited n = 3 state, the mean energy of the fast atoms, the ratio between the densities of these two groups of atoms and the relative population of the fine structure components of the n = 3 hydrogen state are determined. The atomic temperature is estimated to be equal to the temperature of the excited (n = 3) atoms. The molecular temperature is determined from the analysis of the intensity distribution of the molecular Fulcher-α band and is found to be about two times lower than the atomic temperature.