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BELL SYSTEM TECHNICAL JOURNAL 



12. Reproduction of the British Magnetron 



The problem undertaken at the Bell Telephone Laborator;es immediately 

 after the visit of the British delegation in October 1940 was the reproduction 

 of the 10 cm. magnetron for study and for general radar use at the Bell Labo- 

 ratories and the Radiation Laboratory at the Massachusetts Institute of 

 Technolog>^ The data available were contained in a drawing of a magne- 

 tron having six resonators and in an X-ray photograph of the magnetron 

 used in the demonstration at the Whippany Laboratory, described in the 

 Introduction. The X-ray photograph, reproduced in Fig. 45, showed a 



Fig. 45 — An X-ray photograph of the 10 cm. magnetron oscillator brought to America 

 by a British delegation in October 1940 and copied at the Bell Laboratories. It is the 

 prototype of most magnetron oscillators in the centimeter wave region developed 

 in Great Britain and the United States during the war. 



resonator system having eight resonators. Since this arrangement was 

 known to operate, it was adopted as the starting point for the work here. 



In its first tests at Whippany, the British magnetron was pulse operated 

 at about 10 kv. and 10 amps, peak current. The pulses were of 1 micro- 

 second duration and recurred 1000 times per second. The magnetic field 

 required was about 1100 gauss. The magnetron was loaded with a simple 

 radiating antenna of unknown load impedance. Under these conditions the 

 magnetron generated RF power estimated at the time to be greater than 

 10 kw. 



The eight hole and slot type resonators of the British magnetron were 

 spaced around an anode of 0.8 cm. radius. The resonator system, ma- 

 chined in a block of copper, was 2 cm. long. It was unstrapped, strapping 



