332 BELL SYSTEM TECHNICAL JOURNAL 



these magnetrons are essentially identical. Geometrical and performance 

 data are given in Table III. As may be seen, these magnetrons represent 

 an increase in power capabilities by a sizable factor over the 725A. The 

 4J52 magnetron has been used extensively under the severe conditions of 

 5 yus pulse duration, a repetition rate of 200 pulses per second, 15 kv. and 

 15 amps, input. Under these conditions it has not been possible to elimi- 

 nate entirely a tendency to arc, although good performance is obtained. 



Fig. 74— The 4J52 "packaged" magnetron (100 kw., 9375 mc/s). 



In most respects these magnetrons represent the optimum achieved in 

 magnetron design for wavelengths near 3 cm. during the war. Largely 

 because of the lack of hampering electrical and mechanical restrictions, 

 it was possible to make use of all the latest and best techniques in the design 

 of each of its parts. Thus each possesses the desirable features of "pack- 

 aging," axial cathode mount, wave guide output, and high efficiency at 

 low pulling figure. 



20. Magnetrons for Wavelengths near 1 Centimeter 



20.1 Preliminary Work: Intensive work on magnetrons for wavelengths 

 near 1 cm. began when a joint program with the Radiation Laboratory at 



