The effect of external magnetic field on plasma acceleration in electromagnetic railgun channel

We have studied the effect of an external magnetic field on the dynamics of a free plasma piston (PP) accelerated without solid striker armature in an electromagnetic railgun channel filled with various gases (argon or helium). It is established that, as the applied magnetic field grows, the velocity of a shock wave generated by PP in the channel increases. The experimental results are compared to a theoretical model that takes into account the gas pressure force behind the shock wave and the drag force that arises when erosion mass entering the channel is partly entrained by the accelerated plasma. The results of model calculations are in satisfactory agreement with experimental data. The discrepancy somewhat increases with the applied field, but the maximum deviation still does not exceed 20%.