PLASMA DIAGNOSTIC MEASUREMENTS IN THE CRYOGENICALLY COOLED GLOW-DISCHARGE

Cryogenic cooling is an effective method for the removal of impurity s pecies (water vapour) from the glow discharge. Plasma diagnostic measu rements were performed in order to study the effect of cryogenic cooli ng on plasma processes in the glow discharge source. The fundamental p lasma processes were investigated by using optical temperature measure ments from Fe+ excitation and N2+ rotational emission spectra and phys ical temperature measurements using a thermocouple probe. Fe+ excitati on temperatures were 3500-3900 K. The N2+ rotational temperatures vari ed between 500-620 K, while the thermocouple temperatures varied betwe en 380-430 K. For all the diagnostic measurements, lower temperatures (about 50-300 K lower) were measured for the cryogenically cooled glow discharge system.