Digital position sensitive discrimination for 2-dimensional scintillation detectors

The energy sensitivity of a two-dimensional scintillation gamma detector based on position sensitive photomultipliers has been minimized by a digital differential discrimination unit. Since the photomultiplier gain is position-dependent by /spl plusmn/50%, a discrimination unit has been developed of which the digital upper and lower discrimination levels are set to the position-dependent photomultiplier gain obtained from calibration measurements. Depending on the spatial resolution, there can be up to 65,536 position-sensitive discriminator levels defining energy windows. By this method, narrow discriminator windows can be used for reducing the low and high energy quanta without effecting the sensitivity of the detector. The new discrimination method, its performance and test measurements with gamma rays are described. Further experimental results are also presented.