Arc behavior driven by electromagnetic force between rail electrodes

Observations of arc behavior utilizing a high-speed video camera and measurements of the current flowing in a rail electrode using several pickup coils have been performed to gain information for designing a small bore electromagnetic accelerator. Arc behavior is divided into two modes classified by arc current and the space between insulators in a square bore. A single arc column is found when there is a small arc current and a wide space between insulators (single arc mode). On the other hand, several arc columns appear simultaneously when the current is high and the space between insulators is narrow (distributed arc mode). To effectively accelerate a projectile to a high velocity, it is necessary to maintain a single arc mode and avoid the distributed arc mode which results from restriking between electrodes. The space between insulators proves to be an important factor in the design of hypervelocity and small bore electromagnetic accelerators