Particle Localization by Means of a Scintillation Detector

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Abstract
A cylindrical tube, 8 in. long, 2½ in. in diameter, with flat ends containing scintillation liquid, is placed between two photomultipliers. Neglecting reflection from the side walls, the intensity of light received at a photomultiplier from a scintillation is proportional to the solid angle subtended by the photocathode at the scintillation point. The ratio of two coincident pulses from the two photomultipliers will then determine the location of the scintillation along the tube independent of light intensity or particle energy. The pulse ratio was obtained by feeding one pulse to the vertical deflection plates and the other to the horizontal ones of an oscilloscope and by measuring the inclination angle of the trace. The trace amplitude is related to the particle energy dissipated in the liquid. Preliminary results on the localization effect were obtained using cosmic rays. The coincidence pulse from a Geiger counter telescope perpendicular to the scintillation detector was used to unblank the oscilloscope. Uncertainties resulting from statistical variations of the photomultipliers were measured by means of a light source placed at various distances between the photomultipliers to simulate scintillations. It appears that the localization can be feasibly determined within six percent of the length of the scintillator.