836 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1957 



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

 B=600 GAUSS, B(-=25.6 GAUSS, V=2200 VOLTS, 1 = 38 MA 



Fig. 2 — Typical smooth steep growing-noise patterns, near 4 and 10.7 kmc, 

 respectively, with customary focusing field of about four times the Brillouin value. 

 Collector-ciu'rent traces through small and large apertures reveal decreases in 

 ripple amplitude and increase in average beam diameter. 



