Radiation from a relativistic gyrotron is studied experimentally in the range of 25–29 GHz at a megawatt output power level. Radiation is recorded in the ranges of 126.3 and 146.2 GHz at the fifth cyclotron harmonic. Based on estimates of the signal from the detector, the power of radiation at the fifth harmonic of the gyrofrequency is determined indirectly and found to be –20 dB, relative to the level at the first harmonic.
Ilyakov et al. (Thu,) studied this question.