ENHANCED FREQUENCY AGILITY OF HIGH-POWER RELATIVISTIC BACKWARD-WAVE OSCILLATORS

This paper describes how finite length effects in high-power backward wave oscillators can be exploited in a controlled manner to achieve en hanced frequency agility, Experiments were performed using a Sinus-6 h igh-power relativistic repetetively pulsed electron beam accelerator A uniform slow wave structure was used in these studies and its paramet ers were fixed, Sections of smooth-walled circular waveguide of varyin g lengths were inserted both before and after the slow wave structure. Variations in the length of smooth-walled waveguide on the order of a quarter-wavelength of the generated electromagnetic radiation were fo und to significantly affect both microwave frequency and radiation eff iciency in a periodic-like manner, The experimental results were repro duced in TWOQUICK electromagnetic particle-in-cell simulations, A band width of about 500 MHz centered around 9.5 GHz at hundreds of MW power levels has been achieved with constant beam and slow wave structure p arameters.