THE NATURE OF THE WAVES 



407 



QC. Chu and Rydbeck found that under certain conditions gain varies 

 approximately as the \ power of the current. This would mean a slope of f 

 on Fig. 8.11. A f power dashed line is shown in Fig. 8.11; it fits the upper 

 part of the curve approximately. 



-5-4-3-2-1 1 2 3 4 5 



b 

 Fig. 8.9 — The .r's and 3''s with still greater space charge {QC = 1). 



0.25 0.50 0.75 (.00 1.25 1.50 1.75 2.0 



QC 

 Fig. 8.10 — How the gain factor B decreases as QC is increased, for the value of h which 

 gives a maximum value of x\ . 



If we examine Figs. 8.7-8.9 we tind that for large and small values of b 

 there are, as in other cases, a circuit wave, for which y is nearly equal to 

 — b, and two space-charge waves. For these, however, y does not approach 

 zero. 



Let us consider equation (7.13). If b is large, the first term on the right 

 becomes small, and we have approximately 



a = ±j2\/QC (8.28) 



