Gamma Ray Pattern Analysis by Fast Scintillation Timing

A position sensitive detector is needed for gamma ray pattern analysis and in this study the usual pulse height method has been replaced by the transit time method using the time of flight principle. Two photomultipliers were attached to the ends of a plastic scintillator rod and the time delay between the observed signals was recorded and converted into a position reading. The position resolution was measured by using a narrow collimated gamma ray beam penetrating the rod transversally at a certain position. The transit time difference from the scintillation position to each photomultiplier was measured with a positron lifetime spectrometer giving a position resolution of between 11 mm and 23 mm. The results of the measurements and relevant applications have been discussed including the positron camera and angular correlation apparatus.