Chaos in gas discharges

Summary form only given. Potential relaxation oscillations in filament cathode discharges at very low pressure is examined by comparing experimental results from different discharge arrangements with particle-in-cell simulations and with a model based on the van-der-Pol equation. The filament cathode discharge has two stable modes of operation: the low-current anode-glow-mode and the high-current temperature-limited-mode, which form the hysteresis curve in the I(U) characteristics. close to the hysteresis point of the AGm, periodic relaxation oscillations occur. It is demonstrated that the AGM can be understood by ion production in the anode layer, stopping of ions by charge exchange, and trapping in the virtual cathode around the filament. The relaxation oscillations consist of a low filing phase and a rapid phase that leads to formation of an unstable double-layer, current-spiking, and ion depletion from the cathodic plasma. The relaxation oscillations can be mode-locked by external modulation. Inside a mode-locked state, a period doubling cascade is observed at high modulation degree.