Helix type traveling wave tube

Abstract

A helix-type traveling wave tube delay line extends from an input side to an output side. An electron gun adjacent the input side of the helix means transmits an electronic beam to a collector adjacent the output side. An attenuator divides the helix at a location between the input side and the output side. Between the attenuator and input, the helix has a pitch (P.sub.0). Between the attenuator and the output, the pitch (P.sub.1) of the helix is greater than the pitch (P.sub.0) to form a fast velocity circuit. The pitch (P.sub.2) of a second part of the helix between the attenuator and output is less than the pitch (P.sub.0) to form a slow velocity circuit. A third part of the helix is interposed between the first and second parts to form a velocity taper section having a helical pitch which varies from the larger pitch (P.sub.1) to the smaller pitch (P.sub.2). One fairly central position in the third part of the helix has an average pitch of (P.sub.1 +P.sub.2)/2. A first length (L.sub.1) of the helix includes all of the first part and continues to the position of average pitch. A second length (L.sub.2) of the helix includes all of the second part and continues to the position of average pitch. The ratio L.sub.1 /L.sub.2 ranges from 0.6 to 2, and the ratio (2(P.sub.1 -P.sub.2)/(P.sub.1 +P.sub.2)) of the difference between pitches P.sub.1 and P.sub.2 to the average pitch ranges from 0.04 to 0.14.