The high-power pulsed magnetron: a review of early developments

After outlining the main trend of magnetron development before the war, with particular reference to the factors which played a part in its rapid progress during the war, the paper describes the events leading to the development, in June 1940, of the first high-power pulsed magnetron for a wavelength of 10 cm. The multi-resonator system developed by Randall and Boot at Birmingham University and the large oxide cathode developed by Gutton in Paris for a different type of magnetron were combined in a construction, designed for use with a small permanent magnet, which met the requirements for airborne service and was suitable for quantity production. The result of these steps was an immediate increase in pulse power and life by a factor of at least 10, with a similar reduction in magnet weight. The systematic development of design procedures, based on pre-war work, played a major part in the 100-fold increase in pulse output power at 10 cm, which was achieved between June and December 1940. The fundamental difficulties of multi-segment magnetron design were, however, only beginning to be appreciated at the end of this initial period of rapid expansion and, by comparison with modern knowledge, the ideas of that period and the technique available for experimental study were very incomplete. A companion paper provides a review of some of the vast amount of work which still remained to be done after the close of the phase with which the present paper deals.