GB668334A - Improvements in very high gain travelling-wave valves - Google Patents

Abstract

668,334. Travelling-wave tubes. COMPAGNIE GENERALE DE TELEGRAPHIE SANS FIL. Aug. 3, 1949 [Sept. 17, 1948], No. 20265/49. Class 39 (i). A travelling-wave amplifier comprises a plurality of separate systems, each comprising a cathode, an electron beam, and a retardation line, the wave travelling along the retardation line of at least one of the systems interacting with the beam of the next system so that the total gain of the valve is divided between a number of stages operating in cascade. In one form, Fig. 1, electron beam F1 from cathode K1 amplifies the input wave applied to helix H1 and the amplified wave modulates a second beam F2 from cathode K2 which generates a still farther amplified wave in helix H2. The beam F2 passes outside the helices H1, H2 and may or may not be annular. The cathode K2 may be correspondingly annular, broken if necessary by the quartz rod or rods T1. Coatings of high-frequency loss material R1, R2 on the quartz rods T1, T2 or on the wire of the helices H1, H2 terminate the helices non-reflectively and the helix H1 may be provided with further loss material at A. Magnetic focusing is employed. In a modification, Fig. 2 (not shown), beam F2 passes first between helix H1 and the envelope which is of metal and then inside helix H2 and interacts with the transverse field component to produce gain. The collectors C1, C2 of Fig. 1 are combined into a single collector to facilitate cooling of, and D.C. supply to, collector Cl. The devices may have more than two amplifying stages in cascade. The devices may be used as repeaters in transmission systems. Prior art repeaters comprising a number of travelling-wave tubes connected in cascade are referred to.