Nonlinear dynamical behavior of thermionic low pressure discharges. II. Experimental

Strongly nonlinear relaxation oscillations of discharge current and plasma potential are investigated in a magnetized thermionic plasma discharge. The quasi‐one‐dimensional electron motion allows a direct comparison with one‐dimensional models and computer simulations. Two different stable discharge modes can be established, the low‐current space charge limited and the high‐current temperature limited mode. Time resolved probe measurements of the plasma potential distribution demonstrate that the current oscillations result from a strongly nonlinear instability of the potential structure in the weak current discharge mode. This confirms the model based on particle‐in‐cell simulations [F. Greiner et al., Phys. Plasmas 2, 1810 (1995)]. The oscillation process consists of three distinct phases. The sequence of events and the observed parameter dependencies of the oscillation frequency is in accordance with the model. The periodically driven system shows the characteristic behavior of nonlinear oscillators: q...