Simultaneous alpha and gamma discrimination with a phoswich detector using a rise time method and an artificial neural network method

Abstract

We used two digital methods—rise time discrimination (RTD) and an artificial neural network (ANN)—to simultaneously discriminate alpha particles and gamma rays detected by a phoswich detector (50 μm BC-400 coupled to 3 mm CsI(Tl)). The results for 10,000 pulses discriminated by the RTD method showed that the rise time distribution of the pulses is rather vast (between 200 and 800 ns for gamma rays and less than 40 ns for alpha particles). The same result was also observed in the dual-parameter diagram (pulse rise time versus area under the pulse) for an 241Am source. Then, as another approach, three pulse features—rise time, pulse height ratio, and charge ratio—were extracted from 2000 pulses to be used to train an ANN. The trained ANN was used to discriminate 10,000 pulses. By comparing the discrimination performed by these two methods, we concluded that the ANN method had much better performance. The spectroscopy results for 137Cs and 241Am sources in front of the detector also showed that the ANN method is suitable for discrimination.