Development of a high current pseudospark switch and measurement of electron density

The pseudospark, a low-pressure gas discharge in a special geometry, is suitable for high-current switching. A single-channel prototype is tested with a 3.3- mu F capacitor bank, voltages up to 30 kV, and peak currents up to 120 kA. The electrical circuit, not comprising any load resistor causes weakly damped sinusoidal pulses of 5- mu s duration at 90% current reversal. For lifetime tests, a switch with an alumina insulator and copper seals is used. Hydrogen is the working gas. Several electrode materials like molybdenum, tungsten, graphite and chromium-copper are tested. Optical investigations of the discharge and of plasma parameters are done with an O-ring sealed pseudospark switch. The light of the discharge is observed spectrally integrated with a streak camera. Spectral resolution is obtained by using a high-speed shutter in combination with a monochromator. The radial electron density is determined by measuring the Stark broadening of the Balmer H/sub beta /-line. At 60 kA a maximum electron density of about 2*10/sup 17/cm/sup -3/ is calculated.<
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