Large orbit gyrotron at submillimeter waves

A successful operation of a large orbit gyrotron (LOG) at submillimeter waves has been demonstrated. The LOG utilized a 250 keV/4A/10 μs axis-encircling electron beam produced by a thermionic-emission electron optical system. The third cyclotron harmonic, single-mode oscillations at the frequencies of 371 GHz and 414 GHz for TE_3,8 and TE_3,9 modes, respectively, with a power up to 10 kW have been measured. Using a cavity of smaller diameter, the LOG operation at the TE_3,5 mode at the frequency of 369 GHz with power up to 20 kW was achieved.