Numerical simulation of high-power virtual-cathode reflex triode driven by repetitive short pulse electron gun

Abstract

A virtual-cathode reflex triode is investigated by numerical simulations. A trapezoidal in shape voltage pulse with an amplitude of 300 kV is applied to the solid cathode of the device to drive the cathode negative. The electron beam-to-microwave power conversion efficiency /spl epsiv/, calculated for the pulse flat top with a duration /spl tau//sub ft/=1.2 ns is approximately the same (about 1.5-2%) as well as for a long flat top (/spl tau//sub ft/=4 ns). The simulations show a 10-15% increase of /spl epsiv/ at /spl tau//sub ft/ shortening to 0.6 ns. However, this occurs when the anode mesh transparency is high (80-90%). Considerable enhancement of the efficiency (about four times) for /spl tau//sub ft/=0.6 ns has been calculated if the cathode side surface is brought near to the anode tube (from /spl ap/0.5% at cathode radius R/sub c/=1.6 cm to /spl ap/2% at R/sub c/=3.8 cm). The obtained results would find an application for the design of virtual-cathode reflex triode devices driven by a short pulse and high repetition rate electron gun.