Effects of plasma surface layers on the efficiency of plasma flow switching

The plasma flow switch is a possible fast opening-switch for Z-pinches on inductive-store pulsed-power machines. This paper presents results of two-dimensional, radiation-magnetohydrodynamic models for a well-characterized plasma flow switch operating into a load region at current levels of 5-6 MA. The calculations predict that motion of the switch plasma along coaxial electrodes leads to the formation along the inner electrode of a boundary layer that can interfere with switching. The simulations describe the effect of the boundary layer on switching and show that it may be removed by means of a boundary-layer trap. Predictive calculations were used to eliminate the effects of the boundary layer and led to an improvement in the switch's performance. Comparison with experiments lends credence to the model.