Impulse Streamer Branching from Lichtenberg Figure Studies

Abstract

The Lichtenberg figure technique for the study of the streamer mechanism in the spark transition in positive point to negative plane geometry has been extended to longer gaps. In this extension the phenomena were investigated over a wide range of variables, some of the results of which, including the nature of the figures, the potential of the streamer tips, and properties of negative streamers, are being published elsewhere. This study is confined to the observation of the growth and attenuation of branching in relation to the appearance of the commonly observed solitary spark channel. Featured in longer gaps is the very extensive branching before midgap with decline as the cathode is approached. The luminous primary-secondary streamer sequence observed by the two-photomultiplier technique is an instrumentally conditioned phenomenon resulting from branching. There is no such sequence otherwise indicated by these observations. The same instrumental effect deriving from the branching accounts for discrepancies in the earlier reported values of streamer tip velocities.