GB1470575A - Electron discharge devices - Google Patents

Abstract

1470575 Electron multipliers RCA CORPORATION 28 March 1974 [28 March 1973] 13832/74 Heading H1D An electron multiplier comprises at least two mutually insulated electrodes (e.g. 24, 26) each enclosing an ellipsoidally (e.g. spherical) curved surface of which at least a portion is electron emissive, one electrode 26 having an inlet area 46 and outlet area 47 defined at least in part by the electrode structure, the latter area being between the inlet area and the emissive area opposite inlet area 46, the other electrode 24 having an outlet area 53 which is larger than inlet area 46. The inhibition of undesired effects is detailed and improved collection mechanisms discussed in terms of penetrating accelerating fields which conform to the shape of the internal electrode surface. The multipliers may be used in camera tubes (e.g. orthicon) or photomultipliers, the electron source may be a photocathode or thermionic cathode, and the multipliers may detect e.m. radiation such as light, or nuclear radiation. In Fig. 1, the electrodes 24, 26, 28, 30 are mounted between ceramic spacers 20, 22, by extensions 48 (Fig. 2), the latter three electrodes may be 0À005 to 0À010 inch thick Cu-Be having secondary emission characteristics, and member 51 of electrode 24, adjacent mesh member 52, may be 0À010 inch. Ni-Ag or Mo carrying photoemissive coating 50 (e.g. alkali metal activated antimony). A poorly emissive material (e.g. Ni) may react with or be coated by deposited materials to be photo emissive or secondary emissive, or a material such as ceramic may be moulded and provided with a deposited layer. Electrode diameters and opening sizes are specified. The line of centres α may be 90 to 70 to 110 degrees, the apertures are preferably circular, but, as indicated in phantom at 49 in Fig. 2, the intermediate portion may be removed to create a single aperture. In this ease the inlet and outlet areas are defined by the co-operation of the two electrode structures. The electrode centres may be in a common plane or helically or otherwise disposed, e.g. electrode 24 may be centrally located with the other electrodes in series around its periphery. A conductive wire grid or mesh may be fixed over inlet aperture 46 to increase field penetration, and aperture 46 may have a collar or post projecting into the outlet of the preceding electrode.