Performance of a three-cavity gyroklystron

The Naval Research Laboratory (NRL) is investigating the gyroklystron amplifier (GKA) concept. The purpose of this program is to assess GKA characteristics in order to determine if a microwave tube is capable of achieving the high efficiency, gain, and output power predicted by numerous theories. The first in a series of tubes to examine GKA behavior has been fabricated and is currently under test. This tube, GKLY-101, utilizes three rectangular cavities operating in the TE101mode. Design specifications include 100 kW output power, 30% efficiency, 40 dB gain, and 4.5 GHz operation (1). Preliminary test results have shown reasonable agreement with theoretical predictions. In particular, perpendicular efficiencies as high as 60% have been observed. The largest output power, to date, has been 51 kW. These results suggest that the desirable characteristics which have been predicted for the GKA can be realized with a microwave tube.