_(a) 



(b) 



c) 



(d) 



10 



12 



14 



16 



18 



Z IN INCHES ALONG DRIFT TUBE (0 IS 0.95" FROM ANODE) 

 B=279 GAUSS, Bc=1.19 GAUSS , V=2200 VOLTS ,1=38 MA 



Fig. 3 — At about half the focusing fields used in Fig. 2, the growing-noise 

 pattern is much the same at 4 kmc, but shows significant articulation at 10.7 

 kmc. The collector-current traces show pronounced decreases in ripple amplitude, 

 and differences in ripple patterns obtained with different apertures. 



837 



