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16 



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

 B=134.7 GAUSS, 8^=18.24 GAUSS , \/=2200 VOLTS, 1 = 36 MA 



Fig. 5 — The magnetic fields in drift tube and at the cathode have been adjusted 

 empirically to expand the growing-noise region over the entire drift region, with 

 the L.O. at 3,990 mc. The field is slightly less than the Brillouin value, but the 

 beam is strongly rippled because the gun was designed for best focusing at a much 

 higher field. The noise-current maxima align with the average collector currents 

 on their increasing slopes, for all three aperture sizes. 



840 



