Design and performance of a high power pulsed magnetron

This paper deals with the development of a magnetron to generate multi-megawatt pulsed r.f. power. Specifically discussed are the design and operating characteristics of pulsed magnetrons which have been built and tested at 1310 mc/s in the voltage range of 50 to 75 kilovolts and have delivered power outputs of the order of 10 megawatts at 10 microseconds and 0.0017 duty. These tubes are the first pulsed magnetrons known to deliver this much power and, as far is known, have delivered higher pulsed power at this duty and pulse width than any other tube at any other frequency reported in the literature. There was little previous knowledge or experience available for guidance. Among the most important problems which had to be solved were: 1. Establishment of reliable criteria of π-mode stability as guides for high power magnetron design; 2. Development of a wide bandwith r.f. window which would permit operation of the tube at full power in air at atmospheric pressure; 3. Development of a cathode capable of withstanding high back bombardment power with reasonable life; 4. Development of methods for fabricating a large magnetron; 5. Elimination of voltage breakdown in various parts of the magnetron; 6. Generation and measurement of 1 to 10 microsecond pulses at about 100 kilovolts and 400 amperes; 7. Development of a calorimetric load of thermal capacity for testing the magnetron at full power.