264 BELL SYSTEM TECHNICAL JOURNAL 



PART II 



DEVELOPMENTAL WORK ON THE MAGNETRON OSCILLATOR 

 AT THE BELL TELEPHONE LABORATORIES, 1940-1945 



1 1 . General Remarks 



IN THE first part of this paper the fundamentals of the theory of the 

 magnetron oscillator have been discussed. The objective has been to 

 establish for the reader a general picture of the nature of the electronic 

 mechanism and of the role played by the RF circuit and load. 



In the second part of the paper is traced the research and development 

 work done at the Bell Telephone Laboratories on the magnetron oscillator 

 during the war years, 1940-1945. The effort was directed, for the most 

 part, toward the development of magnetrons to meet definite radar needs. 



Fifteen different types or families of magnetrons were developed at the 

 Bell Laboratories during the war. Included among these are some 75 

 separate Western Electric Company or RMA code numbers. It has been 

 found most convenient to discuss the work done on each type of magnetron 

 as a unit, although, to be sure, there has been considerable interplay between 

 projects. Something is said of the origin of each type, of the problems en- 

 countered in its development, and of the solution of these problems, in some 

 cases involving studies and experiments of general interest. Special charac- 

 teristics and general performance data for each type of magnetron discussed 

 are given. Included also is a general discussion of the work done on mag- 

 netron cathodes, which, although carried out on specific magnetrons, has 

 been of general applicability to all. 



Before proceeding with the detailed discussion, it would be well for the 

 reader to recognize the general scope of the work to be described and the 

 general nature of the problems encountered. The work of the Bell Labora- 

 tories in the development of pulsed magnetrons for radar use has extended 

 over practically the whole range of effort surv^eyed in the Introduction. 

 Work has been done throughout the range of wavelengths from 45 cm. to 

 1 cm. and on magnetrons capable of developing over one megawatt peak 

 RF power. It has included work on such features as tuning, coaxial and 

 wave guide outputs, several types of resonator systems and strapping 

 schemes, and on the incorporation of the magnetic circuit IdIo the magnetron 

 structure in so-called "packaged" types. 



The scope of the developments to be described may be judged from 

 Figs. 41, 42, 43, and 44. That part of a magnetron oscillator which perhaps 

 best gives one an idea of size and wavelength range is the resonator block. 

 In Fig. 41 is shown a series of resonator blocks ranging in resonant fre- 



