GB862211A - Improvements in or relating to secondary emissive electrodes - Google Patents

Abstract

862,211. Coating by vapour deposition. WESTINGHOUSE ELECTRIC CORPORATION. May 17, 1957 [May 23, 1956], No. 15739/57. Class 82(2) [Also in Groups XXXVI and XL(a)] An electron transmissive type secondary emission dynode for use in a multistage electron multiplier comprises a continuous self-supporting film 32 consisting of a coherent metal oxide or oxides preferably selected from the group of aluminium oxide, magnesium oxide and tantalum oxide. The film can have a thickness of 200 to 500 Angstroms, and be supported by a frame member 34, Fig. 2, of nickel, glass or stainless steel. The film can have a thin electron scattering layer 44 of an evaporated material having an atomic number greater than 25, such as gold, and of a thickness of 20 or 100 Angstroms. The dynode can also have an evaporated continuous secondary electron emissive layer 46 of insulating material such as KCl, NaCl, MgF 2 or MgO, disposed on the film 32, Fig. 3, or on the scattering layer 44, Fig. 4. The layer 46 can be 200 to 500 Angstroms thick. A thin conductive film 48, e.g. of chromium, beryllium or stannic oxide of the order of 100 Angstroms thick, can be evaporated on to the film 32, Fig. 6, or on to the scattering layer 44, Fig. 5. The film 48 can be incoporated in the constructions shown in Figs. 3 and 4, and can be formed as a black deposit by evaporation through an inert gas. The self-supporting oxide film 32 can be made by anodizing a thin metallic foil, a specific example relating to aluminium being described.