The development of a tunable CW magnetron in the K-band region

The development of a low field, K-band, tunable cw magnetron is described. The major characteristics of the device are presented. The research leading towards the development of the magnetron is outlined. This research program had two major objectives: 1) the study of cathode back-bombardment in cw magnetrons, 2) the study of low field operation. The cathode back-bombardment was found to be closely related to two voltage regions at which large anode currents were drawn without any connection to magnetron operation. The close study of these effects made it possible to eliminate them in cw magnetrons through a particular choice of magnetron parameters. The research program culminated in the development of a low field, K-band, tunable cw magnetron, utilizing capacitive Crown of Thorns tuning. At a fixed operating point, an output power exceeding 10 watts at an efficiency exceeding 5 per cent can be obtained over a tuning range of 7 per cent. The tuning range can be doubled by lowering the output power requirements and making use of two operating points.