Digital Pulse Shape Discrimination in Triple-Layer Phoswich Detectors Using Fuzzy Logic

In this paper, a new pulse shape discrimination algorithm for a triple-layer phoswich detector is implemented and tested. The three-layer detector which was used in this experiment was originally designed for simultaneous detection of beta particles and gamma rays in a mixed radiation field. The first two layers are specifically designed for beta particles and the third layer is designed for gamma-ray interaction. The pulse output of the photomultiplier is digitized and sent to the host computer for further processing. A de-noising algorithm based on the Wavelet Transform (WT) is implemented to reduce the effect of noise introduced by the noisy analog channel and by the photomultiplier tube. Three new timing features were extracted and given as input to a fuzzy interface system (FIS). The FIS output indicates to which scenario the input signal belongs. Compared to the non-fuzzy method which was initially implemented for this detector, the fuzzy algorithm shows a better performance in separating beta and gamma spectra, especially at high energies. Also, fewer pulses are rejected, due to classification as unknown pulses, and interaction in multiple layers is detected more efficiently.