GB782768A - Improvements in or relating to travelling-wave tubes - Google Patents

Abstract

782,768. Travelling wave tubes. SIEMENS & HALSKE AKT.-GES. May 10, 1955 [May 11, 1954], No. 13510/55. Class 39(1). The slow wave structure of a travelling wave tube comprises a wire or strip wound in a plurality of helical turns having inductive portions 4, Fig. 2, and capacitive portions 5, 6, the capacitive portions only lying in the region of energy exchange with the electron beam 9 or beams and the inductive portions being longer than the capacitive portions. The loops 4 may be circular or elliptical. In manufacture, metal wire or strip is wound on a dumb-bell-shaped mandrel after which the mandrel is removed and the turns pulled out to obtain the structure of Fig. 2. Due, however, to the elasticity of the wire or strip used the inductive loops of successive turns are angularly displaced, as shown in Fig. 3, the angular displacement serving to capacitively decouple the inductive loops. The capacitive parts 5, 6 can be bent out slightly to ensure better interaction with the beam which is of circular cross-section, the mandrel having correspondingly outwardly projecting portions. The circumference per turn is approximately equal to the operating wavelength and adjacent parts 5, 6 are of opposite phase. There may be a plurality of electron beams. In further modifications, each helix turn may have four inductive loops and four capacitive portions, Fig. 6 (not shown) or an inductive loop the ends of which are connected by a very small capacitive loop through which the beam passes, Fig. 5 (not shown). In Fig. 5 the circumferential length of a complete turn is one half wavelength, while in Fig. 6 the circumference of a complete turn is twice the wavelength.