Characteristics Of Vhf Discharge N-2 Plasma In Uragan-2m Stellarator

The very high frequency (VHF) discharge for wall conditioning in nitrogen atmosphere is studied. The wall conditioning is applied together with baking. It is driven by the radio frequency (RF) power at the frequency of 130 MHz, higher than that usually used in ion cyclotron resonance heating. The volumetric VHF discharge is successfully ignited and stationary sustained, and plasma occupies most of the vacuum chamber volume. The Langmuir probe measurements give the plasma density and electron temperature. In the optical emission spectrum of the plasma, lines N-2, N-2(+) and the cyano (CN) radical are observed. Possible mechanisms for the formation of the CN radical in the discharge are discussed.