Role of outgassing in surface flashover under vacuum

A. Neuber, M. Butcher, H. Krompholz, L. L. Hatfield, M. Kristiansen

Research output: Contribution to conferencePaperpeer-review

2 Scopus citations


Results of high-speed electrical and optical diagnostics are used as a basis to discuss a new surface flashover model. Outgassing, caused by electron stimulated desorption, is found to play a crucial role in the temporal flashover development. Dielectric unipolar surface flashover under vacuum is experimentally characterized by a three-phase development, that covers a current range from 10-4 A to 100 A. Phase one comprises a fast (several nanoseconds) build-up of a saturated secondary electron avalanche reaching current levels of 10 to 100 mA. Phase two is associated with a slow current amplification reaching currents in the Ampere level within typically 100 nanoseconds. The final phase is characterized by a fast current rise up to the impedance-limited current on the order of 100 A. The development during phase two and three is described by a zero-dimensional model, where electron-induced outgassing leads to a Townsend-like gas discharge above the surface. This is supported by time-resolved spectroscopy that reveals the existence of excited atomic Hydrogen and ionic Carbon before the final phase. The feedback mechanism towards a self-sustained discharge is due to space charge leading to an enhanced field emission from the cathode. A priori unknown model parameters, such as outgassing rate and gas density build-up above the surface, are determined by fitting calculated results to experimental data. The significance of outgassing is also discussed with a view to microwave surface flashover.

Original languageEnglish
Number of pages5
StatePublished - 1999
Event12th IEEE International Pulsed Power Conference - Monterey, CA, USA
Duration: Jun 27 1999Jun 30 1999


Conference12th IEEE International Pulsed Power Conference
CityMonterey, CA, USA


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