Nonlinear effects in the current-voltage characteristic of a low-density Q-machine plasma: I. Related to the potential relaxation instability

We report on an investigation in the magnetized alkaline plasma of a single -ended Q-machine where the current-voltage characteristic of the cold end p late showed some new nonlinear features. The most interesting phenomena are sudden jumps of the electron saturation current which are partly accompani ed by hysteresis. These new phenomena are best visible for low densities. T he current jumps are explained as an indication that the well known oscilla ting nonlinear potential structures, which appear in the plasma column when an electron current is drawn through it, and which are known as the potent ial relaxation instabilities, originate from collective effects of excitati on and ionization interactions produced in front of the cold plate where ac celerated electrons suffer inelastic collisions with the alkaline vapour pr esent in the plasma column.