Gain, saturation, and bandwidth measurements of the NRL gyrotron travelling wave amplifier

Gyrotron travelling wave amplifier (gyro-TWA) experiments have been recently performed, demonstrating linear gains as high as 32 dB at 35.1 GHz for a 70 kv, 9 amp beam, and 24 dB for a 3 amp beam. The gyro-TWA operates in the TE01circular waveguide mode and at the fundamental electron cyclotron frequency. At present, it is a single stage device with no severs or stabilizing elements. The amplifier has been driven into saturation with a maximum observed output of 26 kW at 13 dB gain. Saturation begins at approximately 10 kW output with 30 dB gain. The best efficiency observed was 7.8 percent for a 3 amp beam and 20 dB gain. Linear bandwidth measurements show a -3 dB bandwidth of approximately 500 MHz for the peak gain of 24 dB with a 3 amp beam.