Railgun electromagnetism

Plasma armatures develop the driving force for accelerating projectiles in hypervelocity railgun applications. We have developed a lumped element description of the distributed plasma armature based on a knowledge of the armature current density distribution. We have also developed an improved technique to extract the armature current density distribution from the rail B-dot signals. Combining our model, the derived current density, and other experimental measurements, we have determined the voltage gradient along the armature, the armature conductivity, and the Lorentz force distribution. We suggest an explanation for the observed armature elongation, the development of secondary arcs, and primary armature separation.<>