Current Jumps and Hysteresis in a Single‐ended Q‐Machine in Connection with the Electrostatic Ion‐Cyclotron Instability

Abstract

A b s t r a c tWe report on an investigation in a single-ended Q-machine where the current-voltage characteristic of a small collector showed some interesting new features. The most interesting of these was a sudden jump of the current at the onset of the electrostatic ion-cyclotron instability. This jump was also accompanied by hysteresis. Besides that, the characteristic showed another trivial type of hysteresis that was only due to a temporary covering of the collector by alkaline metal from the plasma. The former phenomenon could be an indication that the .well .known nonlinear potential structures that appear periodically in front of the collector during a cycle of a high-amplitude electrostatic ion-cyclotron instability, are related to inelastic collisions of accelerated electrons with alkaline vapour present in the plasma column.

Nonlinear Effects Related to the Simultaneous Excitation of Three Instabiities in Magnetized Plasma

“…The association of the current jumps and hysteresis effect with the appearance of EICI and PRI was already observed [11][12][13][14]19]. Here, we recorded the same phenomena also in relation with the onset of the KHI.…”

“…For exciting the PRI, the radius of the collector has to be equal or larger than that of the plasma column, so that the ion trajectories can be considered as one-dimensional [7,8,11,12]. For exciting the EICI, the radius of the collector must be considerably smaller than that of the plasma column, but still in the range of a few ion gyroradii [5,[13][14][15]. The Kelvin-Helmholtz instability (KHI) appears at the interface between two adjacent flow regions with a velocity shear [3,4,16].…”