Research On The N/γ Discrimination Method Based On Wavelet Analysis

Recently, neutron detection technology has been widely used in different fields. Scintillation detectors always exhibit a strong insensitivity to neutron and γ ray, it is of great value to discriminate neutrons and gamma-rays(n/γ). A novel algorithm for the discrimination of neutrons and γ-rays with wavelet transform modulus maximum(WTMM) in an organic scintillation has been proposed in this paper.It was validated the validity and feasibility of the WTMM method on the way of simulation and experimental verification. In the simulation validation, firstly, it was researched the physical character of BC-501 A liquid scintillator for building the model of particle pulse signal of n/γ; Secondly it 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 after WTMM; Finally, the performance of WTMM method was researched by adding different conditions of signal-to-noise ratio white noise to n/γ signals, the results showed that with increasing of SNR more than 11 dB, the error ratios of neutron and γ ray optimized obviously.In the experimental validation, a neutron detection platform including D-T monoenergetic neutron source, BC501 A liquid scintillation detectors, R329-02 photomultiplier tubes, data collection circuits and computers was build for collecting data. By comparing the de-noising effect of the moving average method, the wavelet threshold de-noising method and the scale modulus maximum trace method, the scale modulus maximum trace method was chosen as the best de-noising algorithm. This technique has been verified by the corresponding mixed-field data assessed by the time-of-flight(TOF) method, the charge comparison(CC) method and the pulse shape analysis(PGA) method. It is shown that the characterization of neutron and γ ray achieved by the discrimination method based on WTMM is consistent with that afforded by the TOF method and better than the CC method and the PGA method. Eventually, a natrue neutron detection platform which comprises a BC-501 A liquid scintillator detector, a R329-02 photomultiplier tube, a high voltage power supply unit and a digital storage oscilloscope was set up to gather the neutrons and gamma rays in the condition of environment, then the effectiveness of this WTMM method was ulteriorly demonstrated.The WTMM discrimination method exhibites a strong insensitivity to noise and holds great potential for digital processing of data from those systems.