GB1191755A - Linear Beam Tube with Plural Cathode Beamlets providing a Convergent Electron Stream - Google Patents

Abstract

1,191,755. Beam-discharge tubes. VARIAN ASSOCIATES. 28 June, 1968 [3 July, 1966], No. 31039/68. Heading H1D. In an electron beam tube a concave cathode surface 2 is provided with a plurality of concave emissive surfaces 6, each aligned with an aperture in an adjacent control grid 7. The surfaces 6 may be of circular outline and the grid apertures may be hexagonal. A similar grid may be disposed on or in the surface of the cathode (Fig. 7, not shown) to inhibit migration of cathode material on to the island portions between adjacent emissive surfaces 6, the apertures in the second grid being aligned with those of the control grid so that beam interception by the control grid is reduced. To form the cathode, the grid 7 is mounted over the spherical surface 3 and a scribing tool is inserted through each of the apertures in the grid 7 to mark its centre; the grid is removed and the concavities 6 are punched into the spherical surface after which the emissive coating is applied. The cathode-grid assembly may be used in a klystron amplifier using electrostatic focusing (Fig. 3, not shown) or magnetic focusing (Fig. 5, not shown) when the magnetic field may be extended to the cathode surface. The gun is also shown in a travelling wave tube employing a helix within an axial focusing electromagnetic field (Fig. 4, not shown) or within a periodic magnetic field provided by permanent magnets (Fig. 6, not shown). The gun may be used for other types of linear beam tubes such as convergent-beam tetrodes, pentodes and triodes.