DISTRIBUTION OF 0.2...4.5 keV PLASMA IONS IN SET OF U-2M DISCHARGES

Abstract

Charge exchange (CX) neutral fluxes were measured by neutral particle analyzer (NPA) in plasma discharges sustained by the W7-X-like radio frequency (RF) antenna in the Uragan-2M (U-2M) stellarator. CX fluxes in pure hydrogen discharge (B0 = 0.36 T, f = 4.926 MHz) in stellarator configuration (effective perpendicular ion temperature TꞱ ≈ 450 eV) is less energetic in comparison with U-2M hybrid configuration (TꞱ ≈ 800 eV). RF discharge in stellarator configuration with helium and hydrogen mixture (B0 = 0.351 T; f = 5.156 MHz, P = 6·10-4Torr) shows more energetic CX fluxes (TꞱ ≈ 1 keV). The ion cyclotron frequency distribution across the U-2M plasma has been studied numerically. These calculations are accompanied by direct measurement of the RF frequency by magnetic sensor. The ion cyclotron frequency is present in plasma bulk of all discharges under consideration.