Secondary arc dynamics in a railgun bore

We have conducted a series of experiments on the growth of secondary arcs in railgun bores. The experimental results indicate that the secondary arc grows bigger as the stored energy of the capacitor bank becomes higher and as the diameter of the railgun bore decreases. The growth of the secondary arc led to the disappearance of the plasma armature in the worst case, which was performed with a small caliber railgun driven by a high stored energy in the capacitor bank. It was found that the spatial distribution of the rail voltage along the bore arc is closely related to the growth of the secondary arcs. The rail voltage at a given point in the railgun bore starts to rise when the plasma armature arrives and after passage it decreased gradually. The region of maximum rail voltage moves with time and propagates from the breech to the muzzle. While the secondary arc, which was far behind the plasma armature, travelled to the muzzle, its motion was considerably influenced by the spatial distribution of the rail voltage. The secondary arc grew only when it moved with the propagation of the maximum rail voltage. When the secondary arc was left behind from the propagation of the maximum rail voltage, it faded gradually or stopped growing.