Experimental Studies of Anode and Cathode Materials in a Repetitive Driven Axial Vircator

Abstract

Repetitive use of a high-power-microwave radiation source implies strong erosion on cathode and anode materials. Electrode-material endurance has been studied in a series of experiments with an axial virtual cathode oscillator powered by a compact Marx generator. The Marx generator is operated in a 10-Hz repetitive mode with a burst of ten pulses. Velvet and graphite was used as electron-emitting materials, and they showed markedly different pulse characteristics. The following three different anode materials were used: stainless-steel mesh, stainless-steel wires, and molybdenum wires, which all had different influence on the pulse characteristics.

Experimental study of a vircator with premodulated electron beam

“…In earlier electrode material studies with an axial vircator it was found that a graphite emitter resulted in lower radiated fields than velvet [6,7], but due to the electrical breakdown problems in this vircator velvet could not be used. One advantage with graphite compared to velvet is that it gives lower shot-to-shot variations Both anode nets were originally made of copper mesh with sharp edges.…”

Design and implementation of dual independent Vircators driven by a single pulsed power source

“…It should be noted that this is only an approximation and studies have shown that the center frequency of vircator operation can be in the range [6], [13]: (8) To determine the correct anode-cathode gap for a particular frequency, experimental results will be taken at various gap lengths for fine tuning. The cavity resonance will then be adjusted accordingly in order to minimize the number of modes in the cavity spacing for a given frequency in an attempt to maximize the efficiency of extracting the high power microwaves.…”

“…Due to the repetition rate of this vircator system and because of the natural deterioration of the anode foil from the beam current, the material will have to withstand the burst pulse operation without being destroyed by continuous operation [8]. Different materials including stainless steel mesh, titanium mesh, and others will be tested to determine which is best for persistent operation.…”

“…The pulsed power system operates up to a repetition rate of 10 pulses per second continuously but can be operated in a burst mode up to 100pps when driving this microwave device. A higher repetition rate would have destructive impacts on the anode foil or mesh and the cathode emitting surface [8].…”

Electrical Circuit Modeling for Efficiency Improvement of Axial Virtual Cathode Oscillator

“…Analysis of the internal phenomena of the vircator is difficult, so experimental research has been the main method of analysis in the past years [1], [2]. However, there is now a tendency to study the process with modeling because of the growing danger of experimental studies that involve increasing microwave output power and input pulse power levels [3]- [5].…”