Experimental demonstration of W-band gyroklystron amplifiers with improved gain and efficiency

The experimental demonstrations of two W-band gyroklystron amplifiers are reported. A four-cavity amplifier operating near 93 GHz achieved 84-kW peak output power and 34% efficiency for a 56-kV 1.4-A electron beam. The measured full-width at half maximum (FWHM) bandwidth was 370 MHz. A five-cavity gyroklystron amplifier produced 72-kW peak output power and 27% efficiency with 410-MHz FWHM bandwidth centered at 93.4 GHz with 50-dB saturated gain. Both amplifiers were zero-drive stable at the operating points. The results from both experiments are compared with theory and good agreement is obtained.