Delay times and jitter in triggered vacuum spark gaps using metal vapor and surface flashover types of triggers

Triggered vacuum spark gap experiments were performed in a demountable arc chamber with a pressure of 10/2 to 10/4 m torr. Planar copper electrodes were used in which one electrode contained the trigger. Metal vapor spark triggers and surface flash-over types of triggers were explored. The delay time between the trigger breakdown and the conduction of the main gap, and the jitter in this time, were measured as a function of main gap voltage ranging from 3 to 20 kV and main gap separations of 13 to 19 mm. Main gap current following breakdown ranged from 3 to 15 kA. Using the metal vapor trigger, delay times as long as 500 ns were observed for a gap field of 500 V/mm while using the surface flashover type of triggers, delay times of 300 ns were observed for a similar main gap field strength. When the trigger was in the cathode electrode and the trigger was pulsed negatively, the operation of the gap was more consistent and the delay times were observed to increase with main gap voltage. The experimental data are interpreted on the basis of plasma expansion models.