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

We 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.