Systematic analysis of a compact terahertz pulse gyrotron oscillator

A compact terahertz pulse gyrotron employing a TE 6,2+ mode interaction to excite broadband terahertz radiation at around 330 GHz has been systematically studied and designed. The manufacture tolerance of magnetron injection gun and nonideal external magnetic field distribution in pulse magnet could affect the transportation of helical electron beam, the beam-wave interaction performance, and particularly the radiation frequency and output wave distribution. Here, we evaluate the gyrotron system from magnetron injection gun, interaction circuit, to quasi-optical mode converter, and provide some necessary guiding data for reference in experimental verification. The frequency-domain results indicate that under the measured magnetic field distribution the threshold of start oscillation for operating TE 6,2+ mode does not exceed the designed operating current 0.5 A., but a certain degree of mode competition arises during wide-range magnetic tuning. The TE 6,2+ mode in gyromonotron state with magnetic tuning range from 12 T to 12.1 T is predicted to be insensitive to the parameter fluctuation of electron beam and generate radiation at 327.3 GHz with quasi-optical conversion efficiency higher than 75 %. On the basis of characteristic analysis and ongoing system assembly, the terahertz-pulse-gyrotron experiment will be conducted in near future.