An Electron-Beam Triggered Spark Gap

The triggering of a high-voltage gas-insulated spark gap by an electron (e) beam has been investigated. Rise times of approximately 2.5 ns with subnanosecond jitter (~0.2 ns) have been obtained for 3-cm gaps charged at voltages as low as 50 percent of the self-breakdown voltage (varied up to 0.5 MV). The switch delay (including the e-beam diode) was 52 ns. The triggering e-beam pulse has a duration of 15 ns and a 0-50 percent rise time of 1.5 ns. The e-beam current is 0.5 kA, and the electron energy can be varied in the range from 80 to 145 keV. The working media were N2, mixtures of N2 and A, and N2 and SF6 at pressures of 1-3 atm. Voltage, current, and jitter measurements have been made for a wide range of gap conditions and e-beam parameters. Variations in the character of the discharge have been inferred using streak and open shutter photography. The photographs show that the discharge has a broad cross section and that its character varies for differing polarites and voltages. The effects of varying the e-beam width and the beam energy are discussed.