GB1494836A - Electron discharge devices - Google Patents

Abstract

1494836 Photomultipliers RCA CORPORATION 29 Nov 1974 [29 Nov 1973] 51813/74 Heading H1D An electron multiplier device comprises photocathode 16, dynode 20, at least one other dynode 22-28 and an anode, the active region of dynode 20 including an area which in crosssection in one plane is of undulating curvature formed by successive regions curving in alternate directions, and in a plane perpendicular to said one plane is rectilinear. In an alternative, electrode 20 is a photocathode. Photocathode 16 is omitted and at least one other dynode is present. Section L1 (Fig. 3, not shown) provides an electrostatic shield and ensures focusing between dynodes 20, 22 and 24, and may be replaced by a separate electrostatic or magnetic focusing structure. The arrangement ensures uniform collection of the electron stream from dynode 20 irrespective of the points of origin. Additional focusing electrodes (e.g. rod 62) may be included and electrostatic or magnetic focusing electrodes (e.g. rod 62) may be included and electrostatic or magnetic focusing may be used. Annular focusing ring electrode 42 is secured to ceramic plates 18a, 18b by tabs 44, 46, characteristics being improved by a tapered geometry (Fig. 5, not shown) and aperture 54 preferably being covered by a focusing grid 43. Semi-transparent photocathode 16 is connected to one of the pins (48), (Fig. 1, not shown) by wire (50) and aluminized coating (52) which provides a shield and electrostatic focusing. Emissive surface 56 may be secondary emissive beryllium oxide on a 0À01 cm. Cu-Be substrate or photoemissive Cs 3 Sb, in the latter case a light permeable grid replacing electrodes 16, and 42. Scan sensitivities are discussed with respect to Figs. 4a, 4b (not shown) and dimensions given. Reference is made to circular cage, elongated staggered, "head-on" and "side-on" type multipliers.