Glow Discharge Cleaning on the Uragan-2M Stellarator

For the stellarator Uragan-2M, a glow discharge system for wall conditioning was developed and installed. The experiments were conducted in the range of discharge currents from 0.025 to 1 A and argon working gas pressures from 0.27 to 13.1 Pa. It is found that the measured current-voltage characteristics are similar to the discharge with a hollow cathode. In the optical spectrum of the glow discharge plasma, Ar lines of the excited atoms Ar I (Ar*) and ions Ar II (Ar^+*) of the main argon gas, as well as the lines of excited hydrogen atoms H I (H*), are observed. The appearance of hydrogen is associated with the desorption of hydrogen from stainless steel because of the interaction of argon with the surface of the vacuum chamber (cathode). The radial profile of plasma density and electron temperature was measured using a movable triple probe. The maximum plasma density was 7.6 × 10¹⁴ m⁻³, and the plasma temperature was 4.6 eV.