Operating characteristics of efficient, high power coaxial gyroklystron amplifiers

We are currently conducting a series of experiments on coaxial tubes which are designed to produce peak powers in excess of 100 MW in X- and Ku-Band. Preliminary results have indicated peak powers in excess of 75 MW at 8.57 GHz in a three-cavity first-harmonic tube with a gain near 30 dB and an efficiency near 32%. In this paper we detail the optimal results of this tube. We also discuss designs and preliminary cold test results of a three-cavity second end-harmonic device, which is expected to give comparable results at 17.14 GHz.