DEVELOPMENT OF A VERY LOW NOISE TRAVELING-WAVE TUBE
Scientific rept. no. 2, 15 Mar-1 Nov 1960
RADIO CORP OF AMERICA HARRISON NJ
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The tube met all of the objective specifications except that for a 2- db maximum tube noise figure. Noise figures as low as 2.6 db were measured on tubes fabricated during this program. The studies on low-noise techniques indicated that two basic mechanisms, operating either separately on in combination, were responsible for the low noise figures obtained. First, beam- cooling effects, based on crossed electric and magnetic fields, decreased tube noise by reducing the axial velocity fluctuations or by converting these fluctuations into a form that would not interact with the signal on the helix. Second, tube noise was reduced by the action of a dense space charge, which tends to dampen or filter space charge waves in a slowly moving stream of electrons. The major design effort consisted of modifying the basic design of the electron gun structure in order to incorporate newly developed noise-reduction mechanisms in the electron gun design.
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