Measurement of the radial metal vapour distribution in a pseudospark switch

Abstract

Radial density profiles of molybdenum vapour in the centre of the electrode gap of a pseudospark switch have been obtained using one-dimensional laser-induced fluorescence imaging. Owing to the random nature of generation and motion of electron emission sites, which are the predominant metal vapour sources, the vapour density distribution fluctuates strongly from one discharge to another. However, from the positions of the maxima of the distribution it can be inferred that emission sites occur primarily on the edges of the cathode hole. Although the absolute number density of Mo vapour emanating from cathodes containing tantalum carbide increases with the tantalum carbide concentration, no marked differences in shape and temporal development of the density profiles can be identified.