REFLEX OSCILLATORS 



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The vital features of the reflex oscillator are the bunching which takes 

 place in the velocity modulated electron stream in the retarding field be- 

 tween the gap and the repeller and the control of the returning phase of the 

 bunches provided by the adjustment of the repeller voltage. The analogy 

 of Fig. 2 explains the cause of the bunching. The retarding drift field may 



Fig. 2. — The motion of electrons in the repeller space of a reflex oscillator may be lik- 

 ened to that of balls thrown upward at different times. In this figure, height is plotted 

 vs time. If a ball is thrown upward with a large velocity of I'l at a time Ti, another with 

 a smaller velocity at a later time To and a third with a still smaller velocity at a still later 

 time Ti the three balls can be made to fall back to the initial level at the same time. 



be likened to the gravitational field of the earth . The drift time is analogous 

 to the time a ball thrown upwards takes to return. If the ball is thrown 

 upward with some medium speed Vo , it will return in some time /o . If it is 

 thrown upward with a low speed Vy smaller than ro , the ball will return in 

 some time /i smaller than /o . If the ball is thrown up with a speed ^2 

 greater than Vq , it returns in some time /o greater than /o . Now imagine 

 three balls thrown upward in succession, evenly spaced but with large, 



