METHOD OF PROVIDING A LAYER HAVING A LOW SECONDARY EMISSION FACTOR ON AN ELECTRON TUBE ANODE

摘要

1350716 Electrode materials PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 18 Aug 1972 [21 Aug 1971] 38631/72 Heading H1D To reduce secondary emission from an electron tube anode with an external Ni surface a dark coloured coating is formed by heating the anode in air at 350-400‹ C., then in a reducing atmosphere at 700-800‹ C. to clean the surface, applying a coating containing Ni and soot and heating to 700-800‹ C. in a reducing atmosphere. The coating is applied by dipping a cleaned Ni coated Fe anode in a suspension of carbonyl Ni in methyl isobutyl ketone and sintering to form a Ni layer. A suspension of soot is sprayed on and the anode finally heated. The soot may be included in the Ni suspension. A pentode comprises a cathode 1, control, screen and suppressor grids 2, 3, 4 and an anode consisting of inner and outer portions 6, 5. The inner portions are coated by the method above, the outer portions which are of aluminized Fe are rendered dark by alloying the Al and Fe or applying a C coating.