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 photocathode is presented. The intended application is to produce spatially uniform current sheet initiation in gas-fed pulsed plasma thrusters. The effect is explained 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 photocurrent spike were unsuccessful probably due to inadequate surface preparation of the photocathode. Infared laser pulses, however, did lead to current production which lead to breakdown from a 15% undervoltage in argon.