Measurements of experimental plasma brush behavior in hybrid armatures

Hybrid armatures used in railguns consist of a conducting link which is commutated to the rails by plasma brushes. The authors describe a set of experiments in which the effects of varying plasma brush parameters including the initial mass of metal foil used to form the plasma as well as the current were studied. The evolution of the plasma brush from a solid metal foil through its melt, vapor, and plasma phase was observed. The resulting brush length and voltage drop were measured. The results of these tests are presented, discussed, and compared to numerical simulations. The experiments have confirmed that a stable plasma can be formed and confined in a hybrid armature brush chamber by magnetic pressure. The experimental results support the numerical simulations which indicate that plasma brushes can be kept short enough to enable reasonably short chambers to be used in hybrid armatures