sekundaerelektronenvervielfacher with coaxial to primaerelektronenquelle arranged prallelektroden

摘要

470,102. Electron multipliers. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., and MYERS, L. M. Feb. 8, 1936, No. 3930. [Class 39 (i)] Electron multipliers comprise several closemesh grids of low work-function interposed in an evacuated envelope between a source of primary electrons and a single output electrode, successive stages of electron multiplication occurring at the grids and the whole, final electron stream being intercepted by the output electrode. The electron emission from a thermionic cathode C is controlled by an openmesh grid CG and is multiplied at successive grids MG1 .. MG' of fine mesh of the order of 200 or more to the inch before reaching the anode A. The multiplying grids are of silver or silver-plated copper oxidized and treated with vapour of alkaline metal such as caesium, rubidium, sodium or potassium, and the other electrodes are of nickel. The electrodes may be cylindrical as shown, or parallel planes, and are supplied from a potentiometer P. Suppressor grids may be arranged in front of the multiplying grids to direct the secondary emission and to reduce back-coupling. In a modification, the cathode is a photoelectric plate transverse to the axis of the cylindrical electrodes. The grid CG may then be omitted or may receive a carrier wave to be modulated according to light variations at the cathode. Specification 454,133 is referred to.