GB975555A - Improvements in or relating to devices for detecting radio-active radiation - Google Patents

Abstract

975,555. Radiation detectors. ELECTRIC & MUSICAL INDUSTRIES Ltd. March 10, 1961 [March 10, 1960], No. 8419/60. Heading G1A. A device for detecting radio-active radiation comprises a casing 1 having an opening, an inwardly directed flange 2 adjacent the opening, resilient material 3, e.g. soft rubber, supported on the flange, a fluorescent screen 4 resting on but not wholly covering said resilient material, a frame 6 surrounding screen 4 and having a dependent wall which presses into the resilient material, a light opaque screen 5, and a protection grille 7 secured to casing 1 and serving to hold screen 5 in light-tight contact with frame 6 and to press the dependent wall into material 3 so as to hold fluorescent screen 4 in position and to form a light-tight closure. The invention is stated to be of general application in radiation detectors of the type which employ a fluorescent screen, but is described more particularly as applied to the scintillation detector described in Specification 975,554 where casing 1 housing a photo-multiplier tube. Where it is desired to detect α radiation, screen 4 comprises a zinc sulphide phosphor deposited on a methyl methacrylate support. Where it is desired to detect both α and # radiation, the screen comprises zinc sulphide in a fluorescent plastic phosphor. Light opaque screen 5 comprises a thin film of beryllium, aluminium or the material known under the Registered Trade Mark "Milinex" suitably aluminised. The grille 7 is surrounded by a frame 7a having a flange 9 on three sides. The centre flange carries a pair of apertured spring fingers (not shown) intended to engage pins projecting from the side of case 1, and the opposite side of the frame is arranged to be secured to the casing by screws. Rubber pressure pads 8 are provided on the underside of frame 7a. If desired opaque screen 5 may be disposed between fluorescent screen 4 and frame 6.