GB806756A - Improvements in or relating to focusing systems for electric discharge devices - Google Patents

Abstract

806,756. Electron beam focusing apparatus; travelling-wave tubes. WESTERN ELECTRIC CO. Inc. June 8, 1956 [June 10, 1955(2)], No. 17786/56. Class 39(1). A beam focusing electrode system consists of an array of wires 16, Fig. 1B, along which the electrons follow, in " Slalom " fashion or sinuously, a neutral equipotential surface 11 or 12 balanced between electrostatic and centtrifugal forces. Electrons may be delivered to both equipotential surfaces. In a travelling- wave tube the array is constituted by the wires of an interdigital or zig-zag delay line or of a flattened helix, or a circular helix may be used with an annular beam. In Fig. 2, the cathode 24 and the collector 26 are in the plane of the wires 21. The cathode 24 is surrounded by an anode 25 and the collector 26 is surrounded by an electrode 27 which is at the potential of the equipotential surface. In Fig. 5 the electron gun 50 is outside the electrode system 51, 52, 53 and the beam is delivered to a tapered section in which both the spacing between outer electrodes 52 and 53 and the spacing between the wires 51 decrease in the direction of travel. The diameters of the wires also decrease. The outer electrodes 52, 53 may be spaced at different distances from the array, may themselves consist of arrays of wires or they may be omitted entirely. The array may be curved instead of linear. In Fig. 9, the anode 98 of the gun and the electrode 101 which isolates the collector 100 have surfaces which lie in the equipotential surfaces 94, 95. The travelling-wave tube may be of the forward or backward wave type and may be an amplifier or oscillator. The electrode system may also be used for beam switching or storage applications by reversing the beam at one point along the array to follow along the other of the two equipotential surfaces, or by trapping the beam between two points of the array. Specification 772,002 is referred to.