SBIR-STTR Award

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.

Keywords:
HIGH POWER MICROWAVE TUBES PULSE SHORTENING RELTRON MICROWAVE TUBE PROCESSING MICROWAVE BREAKDOWN

An experimental program is proposed to further investigate the mechanisms for pulse shortening and to develop in situ tube conditioning techniques that will result in multi-microsecond output operation of the Reltron (Titan Corp.) high power microwave tube. The Phase II effort will refine observation of gas evolution and plasma formation that affect the beam-microwave interaction and that are the causes for pulse shortening in the Reltron. Means to reduce the gas loading in critical tube components, especially the grids, cathode, and beam dump will be developed and implemented on a Reltron testbed. The ojective is to demonstrate demountable and interchangeable-cavity Reltron operation with a pulse length of 2 microseconds. The development work will include the selection of construction materials and improved vacuum design for the Reltron that minimize gas evolution during the power pulse. It will also include in situ cleaning and degassing of the cathode and grids by Ohmic, discharge, and radiative heating and by electron beam desorption. Use of the techniques to obtain several microsecond pulse duration in tubes of interest for commercial applications will also be investigated.

Keywords:
RELTRON HIGH POWER MICROWAVE TUBES MICROWAVE BREAKDOWN MICROWAVE TUBE PROCESSING PULSE SHORTENING