Arc Ignition

Low energy surface flashover for initiation of electric propulsion devices

“…One of the central part of electrical propulsion systems are ignitor subsystems, which are required for the discharge initiation. Generally, there are many different methods to ignite a discharge in vacuum, among which are initiation using gas injection, high voltage breakdown, mechanical actuators for drawn arcs, and fuse wire explosion [20,26,27], etc. Other methods such as the triggerless method use vaporization of conductive coating between the anode and cathode [28].…”

“…While the triggering methods considered above are capable of discharge initiation, they have significant drawbacks from the prospective of propulsion applications. Indeed, the necessity to carry a gas storage tank for the gas injection triggering methods [26], and the need to utilize a high voltage source in high voltage breakdown techniques [20,27] are adding to weight and complexity of the ignitor. Use of the fuse wire explosion for the discharge ignition is highly unreliable if multiple ignitions are expected [27].…”

“…Indeed, the necessity to carry a gas storage tank for the gas injection triggering methods [26], and the need to utilize a high voltage source in high voltage breakdown techniques [20,27] are adding to weight and complexity of the ignitor. Use of the fuse wire explosion for the discharge ignition is highly unreliable if multiple ignitions are expected [27]. The triggerless approach suffers from electrode/film assembly damage after relatively low number of triggering events 1,000 -10,000 [29].…”

Preparation of Zinc Oxide Thin Films by Reactive Pulsed Arc Molecular Beam Deposition

“…The emission has been shown to start at “whiskerlike” surface imperfections with an approximately 0.5 micron radius on the cathode surface. The electric field can be 2 orders of magnitude larger than the average field of the cathode on these imperfections . With these enhanced local fields, some electrons will spontaneously tunnel into the vacuum.…”

“…When a critical current density, about 10 12 A/m 2 , is achieved at a whiskerlike emitter or triple junction, joule heating causes the cathode material to melt, sublimate, and evaporate . With a high local pressure of sublimated material and free electrons to ionize the background gas, a cascade of primary emission electrons, secondary electrons, and sublimated electrode materials is accelerated across the electrode potential gap to the anode.…”