DIGITAL POSITION-SENSITIVE DISCRIMINATION FOR 2-DIMENSIONAL SCINTILLATION DETECTORS

The energy sensitivity of a two-dimensional scintillation gamma detect or based on position sensitive photomultipliers has been minimized by a digital differential discrimination unit. Since the photomultiplier gain is position-dependent by +/-50%, a discrimination unit has been d eveloped of which the digital upper and lower discrimination levels ar e set to the position-dependent photomultiplier gain obtained from cal ibration measurements. Depending on the spatial resolution, there can be up to 65,536 position-sensitive discriminator levels defining energ y windows. By this method, narrow discriminator windows can be used fo r reducing the low and high energy quanta without effecting the sensit ivity of the detector. The new discrimination method, its performance and test measurements with gamma rays will be described. Further exper imental results are also presented.