PART I — THE GROWING NOISE PHENOMENON 



845 



Figs. 2 and 3, except possibly for the 10.7 kmc noise current in Fig. 3 

 (at a relatively low magnetic field). 



To establish a connection between the two types of noise growth, the 

 noise record of P'ig. 6 (for 10.7 kmc with greatly expanded gain region) 

 is compared with that near -4 kmc under the same conditions, in Fig. 7. 

 The growing noise region for 4 kmc does not start until at least four scal- 

 lop wavelengths past the earliest observed 10.7 kmc noise growth. More- 

 over, the 4-kmc noise pattern resembles that for 10.7 kmc in many de- 

 tails. (The resemblance in details of noise patterns at nearby frec^uencies 

 has been remarked before, in connection with Fig. 4.) 



cr 



UJ 



o 



Q. 

 LU 



<n 



o 



z 



liJ 

 > 



_l 



LU 



(a) 



50 

 45 

 40 

 35 



30 

 25 

 20 

 15 

 10 

 5 





 50 



45 



40 



35 

 30 

 25 

 20 

 15 

 10 

 5 



2 4 6 8 10 12 14 16 18 



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

 8=260 GAUSS, Bc=31.2 GAUSS, V = 2200 VOLTS, 1 = 38 MA 



Fig. 7 — The pattern of growing noi.se in Fig. 6, near 10,690 mcs, is compared 

 with that near 3990 mc for the same fields. The gain region of the latter curve 

 starts much later and is much smoother than the former. The small irregularities 

 on the 3,990 mc curve resemble the scallops of the 10,690 mc curve, in a blurred 

 way. 



Cb) 



