A high harmonic gyrotron and a gyro-peniotron with an axis-encircling electron beam and a permanent magnet

A gyrotron with an axis-encircling electron beam (LOG) is useful for high frequency operation, because the high beam efficiency is kept even at high harmonic of electron cyclotron resonance. We have designed and constructed such a gyrotron with a permanent magnet. The gyrotron has already succeeded in the operations at the third, the fourth and the fifth harmonic resonances. The operation frequencies are 89.3 GHz, 112.7 GHz and 138 GHz, respectively. Operation cavity modes are TE₃₁₁, TE₄₁, and TE ₅₁₁. A gyro-peniotron which operates at the tenth harmonic is being designed. In the case, we are using the same facilities as those of LOG mentioned above. The advantage of gyro-peniotron is a high efficiency operation even at high harmonics. Computer simulation results indicate that the operation frequency is 280 GHz, the output power around 20 kW, the efficiency higher than 20 percent at the almost same operation condition as those of LOG, that is, the beam energy of 40 kV and current of 2.2 A. We are constructing the whole device and carrying out the operation test.