A SIMPLE PULSE SHAPE-DISCRIMINATION METHOD FOR THE PHOSWICH COUNTER

We have developed a simple pulse shape discriminator (PSD) for applications where a large number of channels are used within limited space and electric power. In the PSD, the output signal from a photomultiplier is differentiated and integrated to form a triple-polar pulse. The time interval between the first and second sero crossings depends on the decay time of the scintillation light. The circuit selects signals from the proper scintillator by using this interval. By this method, we can significantly reduce the effect of time slewing in the low energy region. We have successfully operated sixty four channels of the PSD in a balloon borne hard X-ray experiment.