A simple pulse shape discrimination method for the phoswich counter

The authors 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 zero 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 the effect of time slewing can be significantly reduced in the low energy region. Sixty-four channels of the PSD have been successfully operated in a balloon borne hard X-ray experiment