Broadband electron tuning of frequency in gyrotron with coupled cavities

Potential applications of high-power tunable microwave sources to plasma diagnostics, nonlinear spectroscopy and technology have motivated the efforts to improve the performance characteristics of tunable gyrotrons. In our previous study it has been shown that the band of electron frequency tuning of a conventional high-0 cavity gyrotron coincides approximately with the unloaded cavity pass band which does not exceed 0.1 % usually. To expand frequency tuning band we propose gyrotron circuit consisted of two coupled circular cavities. Nonlinear self-consistent gyrotron theory predicted 15-20 % efficiency and 1.3 % bandwidth in this oscillator. An experimental study of an oscillator with coupled cavities operating in the TE 011 mode at X-band has been carried out. Experimental results of about.1 % bandwidth with an saturated efficiency of about 20 % were achieved and shown to be in good agreement with the theory.