Characteristics of VHF Discharge N2 Plasma in Uragan-2M Stellarator
Yu.V. Kovtuna, V.E. Moiseenkoa, A.V. Lozina, A.N. Shapovala, L.I. Grigor'evaa, V.B. Korovina, E.D. Kramskoya, M.M. Kozulya, G.P. Glazunova, M.N. Bondarenkoa, D.I. Barona, A.A. Bizyukovb, Uragan-2M Team
aInstitute of Plasma Physics of the NSC KIPT, 1 Akademichna Str., 61108 Kharkiv, Ukraine
bKarazin Kharkiv National University, 4 Svobody Sq., 61022 Kharkiv, Ukraine
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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 N2, N2+ and the cyano (CN) radical are observed. Possible mechanisms for the formation of the CN radical in the discharge are discussed.

topics: wall conditioning, radio-frequency discharge, stellarator, slow wave