Stable Operation of a Repetitively Pulsed X-Band Relativistic Backward Wave Oscillator

This letter describes a recent activity in the development of a high-power microwave source based on a modified relativistic backward wave oscillator that is driven by an advanced version of a SINUS-family accelerator using a double-width pulse-forming line insulated with a modern synthetic oil. The relatively compact source of microwave pulses (0.6 GW, 20 ns, 9.4 GHz) can operate at a 100 pps repetition rate in a batch mode with batches of duration up to 15 s. The long-term stability of the oscillator performances during 10^6 pulses was achieved due to the improved conditions for explosive emission of the graphite cathode and the use of a titanium slow wave structure. Both factors prevented the shortening of the microwave pulses. With a proper choice of the magnetic field strength and longitudinal distribution and of the position of the resonant reflector, the pulse-to-pulse deviation of the microwave power was reduced with sacrifice in efficiency, which decreased from a simulated maximum efficiency of 44% to 40% in the simulation and to 35 ± 4% in the experiment. At an accelerating voltage of 418 kV and a magnetic induction of 0.64 T at the cathode, the standard deviation of the microwave pulsed power could be close to the voltage deviation.