35 GHz gyroklystron amplifier development at NRL

Summary form only given, as follows. Experiments on a two-cavity gyroklystron are underway to demonstrate a 140 kW, 35 GHz gyroklystron amplifier, operating at a fundamental beam cyclotron mode and a TE/sub 011/ cylindrical cavity mode. A high power electron beam of 70 kV, 6.6 A is produced from a magnetron-injection-gun which is optimally designed for the TE/sub 01/ mode at 35 GHz. Drift tubes consisting of lossy ceramic rings (80% BeO, 20% SiC) are designed to suppress undesired oscillations. A drive power is injected into the first cavity through a multi-hole coaxial coupler. A capacitive probe is placed directly before the input cavity to measure the beam velocity ratio. Large signal non-linear calculations predict a peak efficiency of 30% (extracted power=140 kW) and a saturated gain of 20 dB over a 0.3% bandwidth at /spl alpha/=1.5, /spl Delta/v/sub Z//v/sub Z/=20% at 13.3 kG and Q/sub 1/=Q/sub 2/=200. Design parameters and initial hot-test results of the amplifier will be presented.