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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.
Sommario
Devices and Related Properties.- The Properties of the Pseudospark Discharge.- Review of Superdense Glow Discharge.- Basic Mechanisms Contributing to the Hollow Cathode Effect.- Cathode-Related Processes in High-Current Density, Low Pressure Glow Discharges.- Comparison of Electrode Effects in High-Pressure and Low-Pressure Gas Discharges Like Spark-Gap and Pseudospark.- Experimental Review.- Mapping and Modeling of the Cathode Fall and Negative Glow Regions.- Emission Spectroscopy in Optically Thick Gas Discharges.- An Analysis of the High Current Glow Discharge Operation of the BLT Switch.- Laser-Induced Fluorescence Measurements of Number Densities of Neutral and Ionized Metal Atoms.- Streamers in Atmospheric Pressure N2: Empirical Results.- Theoretical Modeling.- The Solution of the Continuity Equations in Ionization and Plasma Growth.- Scaling Parameters for Optically Triggered Hollow Cathode Switches Obtained by Computer Simulation.- A Physical Model of Prebreakdown in the Hollow Cathode Pseudospark Discharge Based on Numerical Simulations.- Self-Consistent Models of DC and Transient Glow Discharges.- Weak Collisions in Strong Double Layers.- The Effect of Pendel Electrons on Breakdown and Sustainment of a Hollow Cathode Discharge.- A Two-Electron-Group Model for a High Current Pseudospark or Back- Lighted Thyratron Plasma.- Electron Ionization Rate Coefficients at Very High E/N.- New Applications.- Plasma-Based Device Concepts Based on the Pseudospark and BLT.- Emittance Measurement of a Pseudospark-Produced Electron Beam.- New Ways of Electron Emission for Power Switching and Electron Beam Generation.
Riassunto
Proceedings of a NATO ARW held in Lillehamma, Norway, July 17-21, 1989
