Experimental investigation of W-band (93 GHz) gyroklystron amplifiers

The results from W-band gyroklystron amplifier experiments are presented. Two circuit configurations, WGKL1 and WGKL2, have been demonstrated. The WGKL1 circuit achieved 67 kW peak output power, corresponding to 28% efficiency, for a 55-kV, 4.3-A electron beam. The full width half maximum (FWHM) bandwidth was measured to be 460 MHz, a significant increase over the bandwidth demonstrated in previous W-band gyroklystron experiments. The amplifier was unconditionally stable at the operating point. The WGKL2 circuit, which was designed to have a broader bandwidth, produced 60 kW peak output power at 25% efficiency with a 640 MHz FWHM bandwidth for a 58 kV, 4.2 A electron beam. The results from both experiments are compared with theory and good agreement is obtained.