Velocities of copper and silver ions generated from an impulse vacuum arc

Vacuum gaps with copper and silver needle cathodes were fired by a 13 /spl mu/s duration half-cycle sinusoidal arc, and charge states of the ions were analyzed using the time of flight (TOF) method at different positions in the direction perpendicular to the electrode axis. Velocities of each charge state ion were determined assuming a collisionless flight from the cathode region to the outside of the gap. The velocities of the fastest ions of copper and silver are 2.1 and 1.6/spl times/10/sup 4/ m/s, respectively, regardless of the charge state. The velocities of the ions released with the arc extinction are lower, and differ depending on the state of the charge.