GB967066A - Improvements in or relating to electron discharge devices - Google Patents

Abstract

967,066. Cathodes; semi-conductor devices. WESTERN ELECTRIC CO. Inc. Sept. 22, 1960 [Sept. 28, 1959], No. 32598/60. Headings H1D and H1K. A secondary-electron-emissive or photoemissive cathode comprises a semi-conductive body including a rectifying junction adjacent its surface, this junction being biased in the reverse direction below the avalanche breakdown voltage. As shown, a plurality of such cathodes and a similar photo-cathode 12, Fig. 1, are provided in an electron multiplier. Each cathode comprises a body of semi-conductive material, e.g. silicon, germanium or gallium phosphide, including a thin layer of N-type conductivity adjacent its emissive surface, which may have a caesium coating, and silver shields 16, or, alternatively, these shields may be replaced by extensions of the semi-conductive body. In a further embodiment of the invention, a cylindrical semi-conductive body 43, Fig. 4, mainly of P-type conductivity with a thin outer layer 44 of N-type conductivity, constitutes the secondary-emissive cathode of a multi-cavity magnetron. To initiate operation of the magnetron, a thermionic cathode may be provided adjacent the inter-electrode space, or a portion of the body 43 provided with separate biasing means and having a caesium coating, may be raised to the avalanche breakdown voltage to induce momentary primary emission as described in Specification 830,086, or alternatively the entire cathode may be momentarily raised to the avalanche condition to produce primary emission from a caesium-coated portion of the surface. In both the magnetron and the electron multiplier, the amount of secondary emission may be varied within limits by regulating the bias voltages applied. Specification 521,077 and U.S.A. Specification 2,790,034 also are referred to.