Effects of wall ablation on the internal structure and dynamics of a railgun plasma arc

Summary form only given, as follows. Two kinds of simulation of a railgun plasma arc have been performed using MACH2, a two-dimensional diffusive magnetohydrodynamics code. The simulations are intended to model the arc in the plane of symmetry which intersects the rails and thus effectively model the arc in a gun with infinitely wide rails. Both sets include the effects of magnetic field convection by plasma motion, magnetic field diffusion, energy transport by thermal diffusion, equilibrium radiatio diffusion, and the acceleration of the arc and projectile. The first set of simulations was run without any wall effects to assess the two-dimensional simulation code´s ability to produce certain equilibrium results and natural frequencies of oscillation. These simulations also establish the degree to which the numerical techniques used perturb the one-dimensional solution. In the second set of simulations, the boundary conditions permit energy flux to the rails and to the projectile surface, where a simple ablation model introduces mass at a rate determined by that flux. The internal structure and dynamics of the arc induced by that wall interaction were studied.<>