VACUUM-PLASMA PROPERTIES OF STAINLESS STEEL AFTER IMPACT OF COMBINED GLOW-MICROWAVE DISCHARGES IN ARGON ATMOSPHERE

Abstract

The experiments were carried out to determine the vacuum-plasma characteristics (mainly erosion and outgassing rate in a vacuum) of the stainless steel 12X18H10T before and after processing the walls of the vacuum chamber with the glow discharge and combined, glow-microwave plasma discharges in argon atmosphere. The current-voltage characteristics, the electron density and electron temperature were measured. It was observed that the discharge voltage in the combined regime is significantly lower than in glow discharges. In some modes, this voltage decrease can be up to 200 V. It was shown that erosion of stainless steel 12X18H10T in the combined discharges is 70 %, less than in the glow discharges. Measurements were made of the outgassing rate of 12X18H10T stainless steel with the thermal desorption probe in situ in the DSM-1 vacuum chamber. It was shown that cleaning the chamber wall by the glow discharge during 5 h leads to a decrease in the outgassing rate from 5.5·10-5 to 1·10-5 (Torr.l)/(s.cm2) . When the chamber wall is treated with GM discharge starting from nearly the same initial conditions the outgassing rate decreased to 3·10-6 (Torr.l)/(s.cm2). Spectral measurements of the plasma radiation of a glow and combined discharges show a decrease in the ratio of the peaks of argon ions and neutrals during the transition from a glow discharge to a combined one.