Radial Particle Loss in a Highly Ionized Cylindrical Plasma Column

Abstract

The statistical properties of the plasma fluctuations in a long plasma column produced by a hollow cathode arc discharge show that there exist different states of weak plasma turbulence. The transition between these states occurs as a results of charges in the confining magnetic field, the background gas pressure, and the boundary conditions. Associated with such transitions are radial changes in the plasma confinement. A sudden jump in the radial particle loss rates is manifested by the increase of the current collected by Buchelnikova ring-collectors and by the change in the radial density profiles measured by electrostatic probes. A linear stability analysis identifies the weak turbulence with the unstable electrostatic ion-cyclotron mode. This mode appears to be unstable in the parameter regions where the inverse gradientlength, k,the perpendicular wave number k⊥ and the ion Larmor radius ρH at the sum temperature Te+Ti are related as1/ρH≧k≧ k⊥. The radial particles loss rate predicted by this analysis agrees with the observed one.