GB1039884A - Improvements in or relating to gettering arrangements in velocity modulated electrontubes - Google Patents

Abstract

1,039,884. Velocity-modulated tubes. SIEMENS & HALSKE A.G. May 8, 1963 [May 9, 1962], No. 18128/63. Heading H1D. A velocity-modulated electron tube, e.g. a travelling-wave tube, backward-wave oscillator or a klystron, includes a cathode for emitting electrons, a catcher for receiving electrons from the cathode, means for providing a magnetic field to guide electrons along a path from cathode to catcher and a gettering device in the form of one or more additional electrodes located near to the path and arranged to attract and absorb ions produced by collision of an electron from the cathode with a gas molecule within the tube. In one form, Fig. 1, a travelling wave tube has an anode 6 and Wehnelt cylinder 3 of the electron gun producing a radial field for ions 10, 10<SP>1</SP> which impinge at high velocity upon the Wehnelt cylinder, thus releasing atomized getter material of which the cylinder is formed. The getter material is collected on the anode and the ions absorbed by the active surface formed thereon. Alternatively, Fig. 5, the ions are deflected through a perforated cylinder 8 under the action of a radial field formed between the cylinder and co-operating electrode 9, the ions being absorbed on an active surface produced on the diaphragms 6. In a further embodiment, Fig. 2, the gettering action occurs near the electron catcher, a perforated cylinder 13 being provided adjacent the beam 1. The perforated cylinder in all the embodiments may comprise a wire mesh gauge or a coil of wire. Suitable gettering material is tantalum, columbium, zirconium or titanium.