Investigation and Control of Mechanisms for Pulse Shortening in High Power Microwave Tubes

An experimental program to investigate the mechanisms for pulse shortening in high power microwave tubes is proposed. The Phase I effort will develop diagnostic instrumentation and make direct observations of plasma formation and beam phenomena that are probable causes for pulse shortening in the RELTRON (TITAN Corp.). The diagnostics include measurement of gas evolution from the tube components, especially the grids, cavity gaps, cathode, and beam dump, fast optical observation and spectroscopy of plasma, monitors for beam oscillations, and measurement of cavity electric fields. Experiments are proposed in which different materials will be compared, various degassing techniques applied, and advanced in situ cleaning and conditioning methods attempted. The Phase I objectives are (1) to determine and quantify the causes of pulse shortening in the RELTRON, (2) to identify easier and less expensive techniques than presently used in bakeout and hard tube processing, and (3) to determine the efficacy of techniques for combatting pulse shortening. In Phase II, the effort will further the development of the most effective techniques and use them to extend the pulse duration of the RELTRON and also other HPM sources.