The slow collisional ExB ion drift characterized as the major instability mechanism of a poorly magnetized plasma column with an inward-directed radial electric field

TL;DR

This paper investigates the low-frequency instability in a poorly magnetized plasma with inward radial electric field, highlighting the role of collisional effects and ion drift in the instability mechanism.

Contribution

It provides experimental characterization of the slow collisional ExB ion drift as the main instability mechanism in poorly magnetized plasma columns.

Findings

Unstable frequency decreases with increasing gas pressure.

Unstable frequency varies with magnetic field, increasing at low B and decreasing at high B.

Transition point occurs when ion cyclotron frequency equals ion-neutral collision frequency.

Abstract

The low-frequency instability of a cylindrical poorly magnetized plasma with an inward-directed radial electric field is studied changing the gas pressure and the ion cyclotron frequency. The unstable frequency always decreases when the gas pressure is increased indicating collisional effects. At a fixed pressure, the unstable frequency increases with the magnetic field when the B-field is low and decreases at larger magnetic field strength. We find that the transition between these two regimes is obtained when the ion cyclotron frequency equals the ion-neutrals collision frequency. This is in agreement with the theory of the slow-ion drift instability induced by the collisional slowing of the electric ion drift (A. Simon, Phys. Fluids 6, 382, (1963).