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BELL SYSTEM TECHNICAL JOURNAL 



in Table I. A typical performance chart of one of the series is shown in 

 Fig. 52. The maximum current boundary Hmits the output to values well 

 below those at which other factors, such as cathode dissipation, become 

 restrictive. 



50% 







CONSTANT MAGNETIC FIELD- GAUSS 



CONSTANT POWER OUTPUT- KILOWATTS 



CONSTANT OVERALL EFriCIENCY 



10 20 30 40 50 60 70 



DC CURRENT, I, IN AMPERES 



Fig. 52 — A typical performance chart of a magnetron of the 4J21-25 series 

 mc/s). 



4315 



During operation in the high power, spark gap, line type modulator with 

 which the magnetron was to be used, it was found that the pulse voltage 

 applied to the cathode input leads was sometimes sufficient to cause flash- 

 over. If the arc persisted, vacuum failure from cracking or puncturing of 

 the glass resulted. The external flash-over was accompanied by internal 

 arcs between cathode and anode which were injurious to the life of the 



