Experimental Investigation on Frequency-Tunable Harmonic Gyrotron Based on Axis-Encircling Electron Beam

In this paper, a frequency-tunable harmonic gyrotron based on axis-encircling electron beam is designed and experimentally investigated. By altering the operating magnetic field, the gyrotron can stably operate at the 1st to 3rd harmonics sequentially and possess certain frequency tuning capabilities. With a voltage of 45 kV and a current of 0.7 A, a power of 7.42 kW for fundamental harmonic, 2.9 kW for second harmonic and 0.63 kW for third harmonic are obtained, corresponding to the interaction efficiency of 23.5%, 9.2%, and 1.8%, respectively. Besides, a continuous frequency tuning range of 5.27 GHz and 1 GHz can be achieved for the fundamental and second harmonic oscillations near 160 GHz and 390 GHz, respectively. The good agreement between simulations and experiments demonstrates the accuracy of the measurements, promising in completing the measurements of forth harmonic and achieving multi-band radiation in terahertz band.