Experimental studies of a four-cavity, 35 GHz gyroklystron amplifier

The experimental results from a four-cavity, Ka-band gyroklystron amplifier operating in the(TE)₀₁₁ cylindrical mode at the fundamental of the cyclotron frequency are presented. A peak output power of 208 kW at 31.90 GHz, with a 3-dB bandwidth of 178 MHz (0.5%), an electronic efficiency of 30%, and a saturated gain of 53 dB was obtained with a 72-kV, 9.6-A electron beam at a magnetic field of 12.95 kG and a measured beam velocity ratio of 1.36. The magnetic field was found to have a strong influence on the power-bandwidth tradeoff. At 13.35 kG, a peak output power of 174 kW at 31.90 GHz, with a 3-dB bandwidth of 240 MHz (0.7%), an electronic efficiency of 25%, and a saturated gain of 56 dB was obtained with the same beam parameters. The gyroklystron amplifier was unconditionally stable at these operating points and stability studies are reported. Experimental results were found to be in excellent agreement with large signal simulations.