GB694569A - Improvements in or relating to thermionic valves - Google Patents

Abstract

694.569. Thermionic valves. ENGLISH ELECTRIC VALVE CO., Ltd. Feb. 16, 1951 [March 30, 1950], No. 8050/50. Class 39(i) A thermionic valve comprises a tubular anode surrounding a cathode in the form of a plurality of wires or strips and at least one control grid, which is also in the form of a plurality of wires or strips, interposed between the cathode and the anode, and is characterised by the provision of an additional grid of wires or the like on the side of the cathode remote from the anode and adapted to concentrate the electron stream towards the anode so that parts of the electron stream which would otherwise impinge on the control grid fall on the anode. The additional grid is preferably so positioned that it will operate as required when at cathode potential and it may be connected to the cathode within the valve. The electrodes may be concentric, Fig. 4, with the cathode wires CW equally spaced about a circle, the additional grid wires FGW opposite the mid-points between the cathode wires, the control grid having pairs of closely spaced wires CGW arranged so that a cathode wire is opposite the mid-point between the wires of each closely spaced pair, and the anode A surrounding the other electrodes. Graphs are given showing the reduced grid current obtained with this construction as compared with a similar valve with the additional grid FCW omitted, Figs. 8 and 9 (not shown).