A 500kv triggered spark gap

A triggered spark gap is described to switch circuit impedances of approximately 100 ohm at a potential up to 5OOkV. A switch risetime of 5ns was achieved. The spark gap was pressurised with sulphurhexafluoride and triggered from a 3OkV 50 ohm impedance fast pulse source. A capacitor was used as energy source for switching into the load and was pulsed charged to a nominal maximum of 5OOkV by a separate small Marx generator in approximately 1 microsecond after which the spark gap was triggered. Under these conditions a trigger jitter of 10ns or better was achieved, including the thyratron used as trigger source. On test it was found that reliable triggering of the spark gap could be obtained as low as 30% of the gap self breakdown voltage.