The theory and operation of a multicavity high-harmonic gyro-klystron amplifier

The high-harmonic gyro-klystron relies on the synchronous interaction between axis-encircling electrons and high order azimuthal TEn11cylindrical cavity modes. Harmonic operation-together with RF acceleration of the electron beam constitute a compact moderate to high power millimeter wave amplifier. Experimental results for a fifth harmonic, four-cavity device are compared to theoretical predictions which assess gain, bandwidth, sensitivity to longitudinal velocity spread, self-oscillation and saturation characteristics. A gain of 37 dB has been achieved at the fifth harmonic of the cyclotron frequency. The peak output power was 65 W. The insensitivity of the small signal gain to parallel velocity spread is discussed.