Tilted resonator experiments on a quasioptical gyrotron

Abstract Tilting the resonator axis slightly with respect to the magnetic field axis in the quasioptical gyrotron (QOG) is predicted greatly to enlarge the parameter space available for stable, single-mode operation. Greater interaction efficiency is also predicted for single-mode operation. A resonator with a 2° tilt has been tested on the QOG experiment at the Naval Research Laboratory. The operation of this resonator has been compared to an untilted, but otherwise identical, resonator. Multimode operation of the two resonators was very similar, in contrast to predictions. However, an output power of 600 kW was produced at an efficiency of 8% and a frequency of 120 GHz. At lower power, efficiencies above 12% were observed. The efficiency of single-mode operation appears to be raised significantly by tilting the resonator axis.