Physics and Applications of Pseudosparks

The purpose of the 1989 NATO ARW was to develop applications, and an improved understanding of the physics for high current emission and conduction observed in hollow cathode-hollow anode switches including the pseudo spark and BLT. New applications include highly emissive cathodes for microwave devices, accelerators and free electron lasers, high power tubes, electron and ion beams, microlithography, accelerators, and other plasma devices. Recent research has produced a new generation of gas-phase plasma switches that are characterized by very high current emission and conduction while operating in a glow mode. These switches include the pseudospark and the BLT, both of which have hollow electrodes, switch over 10 to 100 kA peak current, and have cathodes with emission ~ 2 2 10,000 Ncm over ~ 1 cm area. The cathode properties are especially remarkable - about 2 orders of magnitude larger emission than existing thermionic cathodes. Part of the meeting was devoted to understanding these properties, and exploiting applications of this cathode. The remarkable properties of these switches are very surprising in the light of considerable previous work in this area, and these results deserve study in order to understand the underlying physical mechanisms, and to develop ideas and insight into future applications, and foster coherent research in this area. The operating cycle of pseudo-spark and BL T switches and related devices can be divided into four phases: hold-off, triggering, conduction, and recovery. There was very little discussion of the hold-off and recovery phases.