Experimental Registration of Simultaneous Radiation at the First and Third Cyclotron Harmonics in a High-Current Relativistic Gyrotron

We report the experimental studies of radiation on fundamental and third cyclotron harmonic from a Ka-band high-current relativistic gyrotron with a maximum output power of 40 MW. Helical electron beam is formed by the electron optics system based on using the kicker field for initiation of electrons’ gyration and its subsequent pitching in increasing magnetic field. Based on the spectral measurements, we estimate indirectly the radiation power level at the third harmonic of the gyro-frequency as about −30 dB with respect to the first-harmonic radiation level. This estimation is in good agreement with the results of 3-D particle-in-cell (PIC) simulations.