The effect of electrode material on the motion of a plasma piston in rail accelerators

The acceleration of a plasma piston in the channels of rail accelerators with copper and graphite electrodes is studied experimentally. It is found that the plasma velocity is reduced by 15–20% (at equal discharge currents) when graphite electrodes are used instead of copper ones. This may be attributed to an increase in the erosion graphite mass that is drawn into motion by the plasma piston. It is concluded based on the interpretation of the obtained data that the current flow in the channels of rail accelerators is governed at high plasma speeds by the processes of thermoautoelectron emission.