The effect of erosion mass capture on plasma acceleration in electromagnetic railgun accelerators

Results of a series of experiments on plasma acceleration in an electromagnetic railgun accelerator with copper electrodes are presented for various discharge currents and initial pressures in a channel filled with argon or helium. A notion of an effective erosion coefficient is introduced that takes into account that only a particular amount of the erosion mass lost by railgun electrodes during discharge current passage is captured and involved in the motion of accelerated plasma. This coefficient has been calculated in the frame-work of a dynamic model of plasma motion, which includes the force of shock-compressed gas and the drag force that arises when the captured part of erosion mass is entrained by the accelerated plasma piston. It is established that the effective erosion coefficient and the rate of plasma mass variation are weakly nonlinear functions of the discharge current, which also depend on the initial gas density in the railgun channel.