Experimental Demonstration of the Possibility to Expand the Band of Smooth Tuning of Frequency Generation in Short-Cavity Gyrotrons

We show experimentally the possibility to expand significantly the band of smooth tuning of the generation frequency in gyrotrons using cavities that have shorter lengths. Due to a decrease in the sensitivity of the electron-wave interaction process to the spread in the electron beam velocities, one can increase the power of generation at higher longitudinal modes up to a level comparable with the radiation power in the case of excitation of a mode with one longitudinal variation. In this case, overlapping of generation bands at the neighboring longitudinal modes is achieved by increasing the current of the electron beam. In the experiment performed in a gyrotron having an operating frequency of about 12 GHz, we demonstrated a frequency tuning band which exceeded 4% at the kilowatt level of the output radiation power in its greater part. The obtained results open up the possibility of developing tunable high-frequency moderate-power gyrotrons.