Measurement of phase pushing in a 34 GHz harmonic, frequency-multiplying gyro-TWT

A millimeter wave harmonic, frequency-doubling gyro-TWT, is currently being studied and has been demonstrated to produce 100-200 kW peak power at the second harmonic of the electron cyclotron frequency, centered at 33 GHz with a bandwidth of 3% and gain of 20 dB. One goal of this work, in addition to reducing the guiding magnetic field required for cyclotron resonance interactions, is to investigate whether harmonic, frequency-multiplying gyro-amplifiers can produce radiation with better phase coherence than in fundamental devices. We study phase noise in the output radiation to identify the mechanisms responsible for phase fluctuations and seek ways to improve coherence. We present experimental measurements of phase pushing factors and a comparison of the results with numerical calculations of the dependence of phase on technical parameters.