INTERACTION BETWEEN ELECTRON STREAMS 



57 



The variation of gain with frequency under very nearly the same condi- 

 tions as above is shown in Fig. 4. The input signal was in the linear region 

 of Fig. ^. The figure shows a bandwidth of 110 Mc between points 3 db 

 down from maximum. The center of the band is at approximately 255 Mc. 



The currents required to realize the above results are some tenths of a 

 milliampere higher than those used in making estimates of performance of 

 the amplifier, and the voltages for best performance are lower. The use 

 of the actual operating values leads to a prediction of maximum gain at 

 240 Mc for the double-stream interaction in better agreement with the 



40 



30 



150 ZOO 250 300 350 400 



FREQUENCY - MEGACYCLES 



Fig. 4 — Gain versus frequenc>- for double-stream amplifier, operating in linear portion 

 of Fig. 3. 



observed maximum at 255 Mc than the value of 200 Mc originally estimated 

 from the lower currents and higher voltages. Estimated double-stream 

 gain at 240 Mc from theory for the separated hollow beams is 40 db. 



Evidence that the gain of the amplifier resulted from the double-stream 

 interaction was obtained in the following ways: by comparison of the trans- 

 mission through the amplifier with both streams with that for each stream 

 alone, and by comparison of signals obtained from the two identical probes 

 in the electron streams at the ends of the central portion of the tube shown 

 in Fig 1. 



In a typical comparison of the first type, 1 db gain for the device was 

 observed with the inner stream alone. This increased to 29 db when the 

 outer stream was turned on. With the outer beam alone the loss in the 



