Investigation of pulse shortening suppressions on the coaxial vircator

Abstract

Physical mechanism of pulse shorten in coaxial virtual cathode oscillator (VCO) is analyzed theoretically. Anode plasma is one of the most key factors in causing pulse shorten according to the analytical results. Pulse shorten is suppressed based on controlling of generation and diffusing of anode plasma. GW level experiment has been designed to verify the above conclusion. The effects of process treatment of anode, material and grid dimension on the output characteristic of microwave have been studied. A microwave with 840MW output power and 100 ns pulse width has been obtained with 7% power efficiency and 5.6% energy efficiency through optimization of parameters of the device in experiment. Virtual Cathode Oscillator (VCO) is one of promising high power microwave (HPM) sources with its advantage of simple structure, high output power and without guiding magnetic field. Researches show that pulse shorten is very common in most VCO experiment. The physical mechanism of pulse shorten in VCO is analyzed theoretically in this article. The main physical factors that causing the pulse shorten are studied and methods to suppress pulse shorten are proposed. The proposed methods are verified by GW level VCO experiment with 100 ns pulse width.