Plasma diagnostic measurements in the cryogenically cooled glow discharge

Abstract

Cryogenic cooling is an effective method for the removal of impurity species (water vapour) from the glow discharge. Plasma diagnostic measurements were performed in order to study the effect of cryogenic cooling on plasma processes in the glow discharge source. The fundamental plasma processes were investigated by using optical temperature measurements from Fe⁺ excitation and N₂⁺ rotational emission spectra and physical temperature measurements using a thermocouple probe. Fe⁺ excitation temperatures were 3500–3900 K. The N₂⁺ rotational temperatures varied between 500–620 K, while the thermocouple temperatures varied between 380–430 K. For all the diagnostic measurements, lower temperatures (about 50–300 K lower) were measured for the cryogenically cooled glow discharge system.