Generation of 1.5 THz Radiation in a Relativistic Gyrotron Operating in Frequency Multiplication Mode

The frequency multiplication mode in gyrotrons is very attractive for generating radiation in the terahertz range. When moving to relativistic values of the energy of electron flows, the conversion coefficient, which characterizes the ratio of the generation power at high harmonics of the gyrofrequency to the generation power at the fundamental harmonic, increases significantly. In the presented work, generation at the fifth harmonic of the gyrofrequency in a relativistic gyrotron operating in the pulse mode in the 300 GHz frequency range on the TE33.2 operating mode was studied. Initial calculations were carried out using a self-consistent system of averaged equations describing the processes of interaction of the electron beam with a high-frequency field in the gyrotron cavity. At the first harmonic, the interaction with the single TE33.2 mode was considered, and at the fifth harmonic, with the TE 165.7 mode. According to calculations, in the 1.5 THz range the maximum radiation power can reach a power level of 1.5 kW. To analyze the mode competition processes, three-dimensional modeling using the large particle method was performed. Calculations have shown that in the region of maximum power values at the fifth harmonic of the gyrofrequency, a parasitic mode is excited at the first harmonic of the gyrofrequency. As a result, the maximum power at the fifth harmonic is limited to 200 W.