Operation of a Ka-band Harmonic-Multiplying Gyrotron Traveling-Wave Tube

Amplification studies of a Ka-band harmonic-multiplying gyrotron traveling-wave tube (gyro-TWT) are reported. A coupled cavity with inner- and outer-intersecting couplings and precise control of the focusing magnetic field are used to improve the coupling between the fundamental and the harmonic and to adapt the sensitivity of the effect of focusing magnetic field on the beam-wave interaction in the gyro-TWT to high-order mode operation. Experimental results show that 75 kW of peak output power with a bandwidth of 1.06% and a gain of more than 25 dB can be reached at a pulse voltage of 67.2 kV and a pulse current of 15.8 A.