ELECTRON BALLISTICS IX IIIGII-FREQrEXCY FIELDS 



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penetrating the tield to a greater extent and waiting, as it were, for the 

 slower electrons which follow to catch up. The electrons which pass across 

 the gap while the field is becoming progressively more accelerating are 

 spread out. If the retarding field is uniform it can be likened to the earth's 

 gravitational field and the phase-focusing paths on our time-distance plot are 

 parabolas. Figure 9, taken from Pierce's paper, illustrates this while Fig. 

 10 is such a plot taken from the paper by Harrison. One interesting and. 



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Fig. 9 — The gravitational-field analogy to reflex bunching (Pierce). 



Fig. 10 — The phase-focusing diagram for a reflex oscillator (Harrison). 



in a way, unfortunate difference between reflection bunching and direct 

 transit-time bunching is the fact that for reflection bunching the slow elec- 

 trons catch up with the fast ones while the reverse is true for the other type. 

 This means that if both types of bunching are present as shown in Fig. 11, 

 (also taken from Harrison's paper) one will tend to undo the effect of the 

 other. 

 Another way of combining effects of separate bunching actions is to build 



