Possibility of Effective High-Frequency Generation in Low-Voltage Gyrotrons at the Second Cyclotron Harmonic

Despite the high theoretical values of the electron efficiency of the subterahertz gyrotrons working at cyclotron harmonics at low operating voltages, the achievement of acceptable output power levels in such devices is a significant challenge due to the mode competition, the necessity of producing an electron beam with a high current, high ohmic losses in the walls, and the required high accuracy of cavity manufacturing. To solve these problems, we analyze thoroughly variants of low-voltage gyrotrons with conventional cavities and the recently proposed variant of the sectioned cavity, and present a calculation of the electron-optical system for such cavities. It is shown that by ensuring micrometer accuracy of cavity manufacturing at a low operating voltage (5 kV), it is possible to achieve output efficiencies of up to 5% and a power of up to 100 W at frequencies of about 0.4 THz and higher at the second cyclotron harmonic.