Current propagation between a plasma opening switch and a load during opening

Summary form only given, as follows. During the initial stages of opening in a long-conduction-time (/spl sim/ms) plasma opening switch (POS), a current propagation phenomenon is observed between the POS and the load. Experiments carried out on Double at the Institute of Electrophysics (Tomsk) showed that a current channel in the POS plasma is translated downstream for the original plasma region at high speed. Similar results were obtained on DM1 at Maxwell/Physics International and Hawk at NRL. Experiments on Hawk also showed difference in the dynamics of this plasma channel for different conduction times and loads, and between single- and multiple-species POS plasmas. Experiments at the Kurchatov Institute showed similar results in both positive and negative polarity and that the current channel width broadens during propagation. There have been various attempts to explain this phenomenon. Numerical simulations suggest that low-density plasma downstream of the POS location allows for this current channel propagation. Ion emission from the anode also increases the coupling of power to the load. It has also been suggested that lighter ions such as protons in the POS plasma separate from heavy species and are accelerated downstream in a current channel. Finally, it has been suggested that the current channel is a manifestation of nonlinear KMC waves which are predicted within the framework of electron magnetohydrodynamics. In this paper, we review the experimental characterization of this current propagation phenomenon and summarize the models proposed to describe it.