On the limiting throwing velocity of a plasma bunch in a magnetoplasma accelerator

In this paper, we consider some features of plasma bunches throwing in a rail electromagnetic accelerator (magneto plasma accelerator-MPA) associated with the limitation of experimentally achieved muzzle velocity compared to the theoretically expected one. The problem is considered from two points of view: 1) on the basis of a qualitative study of the equations of the one-dimensional steady – state flow of an ideal conductive gas in electromagnetic field and 2) from the point of view of accelerating a current bridge with lumped parameters.
It is shown that the results of qualitative studies of the steady-state gas flow equations are not applicable to the case of plasma bunches throwing in pulsed MPAs, since the theory assumes a continuous effect, in particular of an electromagnetic field, on conductive gas over the entire length of the device.
Using a model of the moving current bridge, implying that the current flows only in a narrow current layer (plasma piston), allow you to accurately reflect the process of its throwing in a MPA until the plasma piston remains compact. Stratification of the plasma piston, secondary breakdowns in the space between the accelerator breech and the piston lead to the cessation of the acceleration process and the transition it to the process described by the model similar to the steady-state flow model.