Digital discrimination of neutron and γ ray using an organic scintillation detector based on wavelet transform modulus maximum

Abstract

A novel algorithm for the discrimination of neutron and γ-ray with wavelet transform modulus maximum (WTMM) in an organic scintillation has been investigated. Voltage pulses arisin g from a BC501A organic liquid scintillation detector in a mixed radiation field have been recorded with a fast digital sampling oscilloscope. The performances of most pulse shape discrimination methods in scintillation detection systems using time-domain features of the pulses are affected intensively by noise. However, the WTMM method using frequency -domain features exhibits a strong insensitivity to noise and can be used to discriminate neutron and γ-ray events based on their different asymptotic decay trend between the positive modulus maximum curve and the negative modulus maximum curve in the scale-space plane. This technique has been verified by the corresponding mixed-field data assessed by the time-of-flight (TOF) method and the frequency gradient analysis (FGA) method. It is shown that the characterization of neutron and gamma achieved by the discrimination method based on WTMM is consistent with that afforded by TOF and better than FGA.Moreover, because the WTMM method is itself presented to eliminate the noise, there is no need to make any pretreatment for the pulses.

Real-Time Signal Processing for Mitigating SiPM Dark Noise Effects in a Scintillating Neutron Detector

“…17). Pile-up pulses were originally extracted using wavelet analysis [52], [54]- [56], [62], [73]- [77]. However, a much simpler way of identifying pile-ups was devised rather than computing wavelet transforms.…”

“…This means that pulse shape discrimination can be used to discriminate neutron signals from other signal types. Various pulse shape discrimination techniques include rise-time comparison [41], charge comparison algorithm [21], [22], [42], [43], digital filters [44]- [47], pulse gradient analysis [48], [49], frequency gradient analysis [50], [51], wavelet analysis [52]- [56], and artificial neural networks [57]- [60].…”

Novel discrimination parameters for neutron-gamma discrimination with liquid scintillation detectors using wavelet transform

“…Sullivan et al used the wavelet transform modulus maximum (WTMM) method for analysis of gamma-ray spectra for isotope identification with low resolution detectors such as sodium iodide detectors [19]. Recently, the wavelet transform modulus maximum technique has been used to discriminate neutrons and gamma rays and found to exhibit better performance as compared to the charge collection method [20]. The performance of wavelet based methods for real time discrimination depends on the expertise with which the method is implemented and availability of hardware resources such as high speed ADCs and FPGAs.…”

“…In liquid scintillation detectors, the relative decay rate of a light output pulse determines the particle type. Hence, these pulses are non-static having different frequency components present at different time instants [20,23]. So a mathematical transform such as the Fourier transform, which is valid only for static signals, cannot reveal the time-frequency features simultaneously [24,25].…”

Toward a fractal spectrum approach for neutron and gamma pulse shape discrimination

“…On the basis of liquid scintillation detectors, many scholars have developed traditional analog circuits such as the zero-crossing method, time rise method and digital charge integration method to attempt to discriminate neutrons and γ-rays. In recent years, with the develop-ment of Digital Signal Processing (DSP) and Field Programmable Gate Arrays (FPGAs) and the wide application of artificial intelligence, digitalized discrimination methods for neutrons and γ-rays, such as the pulse gradient method, neural network method and wavelet analysis method have been developed [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. These methods have led to a great improvement in accuracy in discrimination of neutrons and γ-rays.…”