GB1489810A - Travelling wave tubes - Google Patents

Abstract

1489810 Travelling-wave tubes ENGLISH ELECTRIC VALVE CO Ltd 28 July 1976 [2 Aug 1975] 32421/75 Heading H1D In a travelling-wave tube the slow-wave structure of which comprises a sequence of cloverleaf cavities 2, Fig. 3 (ie. 1, 2, 3, and 4, Fig. 1, not shown), separated by radially slotted, centrally apertured plates of which an example is shown in Fig. 2, permanent magnet material 14 is provided between the inwardly directed noses of each cavity, axially magnetized in opposite senses in adjacent cavities (Fig. 1) to provide a periodic permanent magnet focussing structure which is outside the tube but close to the electron beam. The envelope is formed by the copper walls 15 of the cavities which are brazed to the soft iron coupling plates (5 to 9, Fig. 1). In further embodiments, the half period of the magnetic focussing field is not equal to the length of a single cavity, as in Fig. 1, but to two cavities (Fig. 4, not shown), or three cavities (Fig. 5, not shown), the intervening coupling plates in this case being of copper except for a soft iron outer annulus (22, Fig. 6, not shown) for the radial extent over which the plate is brazed to the neighbouring magnets, in order to couple the latter.