GB1120393A - Improvements in or relating to radiation detectors - Google Patents

Abstract

1,120,393. Radiation detectors. E. K. COLE Ltd. May 6, 1966 [May 6, 1965], No. 19075/65. Heading G1A. A radiation detector arrangement comprises a scintillator made up of an array of discrete sections optically screened from one another, each section being viewed by a preselected number of photodetectors of an array of photo-detectors. When a scintillation occurs in a section, the photodetectors selected to view that section provide output signals whose amplitudes are a function of the position of the scintillation in that section. An array of nine rectangular sections (1-9) Fig. 1 (not shown) e.g. thallium-activated sodium iodide crystal scintillators, have superimposed an array of sixteen photo-multipliers 11-26 Fig. 3 so that four of the latter view each section. The sections are optically separated by thin strips 10 of metal, and this reduces the errors which would occur if an undivided screeen were used, when reproducing an image on the screen of a storage tube corresponding to the position of a scintillation. The outputs of the photo-multipliers are connected to individual amplifiers (11'-26') Fig. 4 (not shown) and resistors (27). The outputs of the amplifiers are connected together in four rows to respective amplifiers (28-31) and four columns, to respective amplifiers (32-35). The outputs (36-43) Fig. 5 (not shown) of these amplifiers are individually connected through pulse lengthening circuits (36'-43') to summation circuits (48-51), and in pairs (e.g. 36 and 37 &c.) to coincidence circuits (44-47). Routing gates (52-55) are also provided in the circuit to divert pulses to a summation circuit which has not received a pulse directly from a pulse lengthening circuit. The summation circuits connect in pairs (48 and 49, 50 and 51) to difference amplifiers (58 and 60) whose outputs (59, 61) control the Y and X deflections of the storage tube. When a scintillation occurs in a particular section 1-9 the output signals from the four photo-multipliers viewing the section will be different depending on the intensity of the scintillation and on how far each is from the scintillation. Since differing energies of radiation incident on the scintillator produce differing scintillation intensities, the images produced on the storage tube are arranged to be for incident radiations of a predetermined energy only, so that errors in the position of the images are avoided. To do this a pulse height analyser (68) Fig. 5 (not shown) receives signals from all the photo-multipliers and controls the difference amplifiers (58, 60) through a pulse lengthening circuit (69), so that only scintillations corresponding to this predetermined radiation level are reproduced. The output of the pulse height analyser (68) is also fed through delay and brightup circuits to initiate writing on the storage tube screen. Any number of sections 1-9 can be used for the scintillator, and in a shape other rectangular e.g. circular.