Progress in experimental studies of harmonic multiplying gyro-amplifiers

Summary form only given. The University of Maryland is investigating gyro harmonic multiplication as a new means of coherently generating high frequency, large bandwidth, high power microwaves with reduced magnetic field, lower noise and high sub-harmonic injection gain. Significant progress has been made in frequency doubling devices. One of them is the phase-coherent harmonic-multiplying inverted gyroklystron (the phigtron), which consists of a Ku-band fundamental gyro-TWT input section, a Ka-band second harmonic two cavity gyroklystron output section and a long radiation-free drift space between them. This device has been characterized as a high performance millimeter wave amplifier with output peak power of 400-720 KW, saturated gain of 30-33 dB, efficiency of 30-35%, bandwidth of 0.3-0.7% and phase stability of 0.026 degree per volt of beam voltage rippling. The second one of our investigations is the Ka-band, frequency doubling, second harmonic gyro-TWT. This traveling wave amplifier utilizes a configuration similar to the phigtron with the only difference in the output section, which is now in the form of Ka-band second harmonic gyro-TWT rather than the simple cavity gyroklystron of the previous case. Preliminary hot test results have been obtained with output peak power of about 180 KW, bandwidth, 3% at central frequency of 32.8 GHz, beam voltage of 50 KV and beam current of /spl sim/30 A. We may bring better test results to the conference after further improving the B field profile and the frequency characteristics of the input coupler.