Laser Discharge Initiation for Gas-fed Pulsed Plasma Thrusters ∗

A method of discharge initiation at an undervoltage by a laser-induced pulse of electrons from a photo-cathode is presented. The intended application is to produce spatially uniform current sheet initiation in gas-fed pulsed plasma thrusters. The effect is ex-plained by a space charge buildup which can increase the electric field of the gap. A theoretical model was developed and showed that an increase of the charge multiplication coefficient to a level above unity will produce a current rise to breakdown. Attempts to use an ultraviolet light pulse to create a photocur-rent spike were unsuccessful probably due to inade-quate surface preparation of the photocathode. In-fared laser pulses, however, did lead to current pro-duction which lead to breakdown from a 15 % under-voltage in argon.