The Simulation Study Of Angular Distribution Of γ-ray In Neutron Elementanalysis By Monte Carlo Method

Neutron Induced Prompt Gamma-ray Analysis (NIPGA) is a kind of determination technology for multi-element instant measurement. With the application of industrial production increasing gradually, experimental design has become gradually mature, and has realized the analysis of abundant elements. Transmission-type methods of determination are used widely, namely neutron source, samples and detectors are arranged in a line and detectors are fixed at the front of sample for receiving the gamma rays. However, this determination method can get the strongestγ-ray count, which is uncertain and lack of theoretical reference. If the detection method used improperly, detector can not receive the maximumγ-ray, which will affect results of measurement, especially for those elements with smaller neutron cross section.In order to improve the measurement method and the measurement accuracy for NIPGA experiments, this paper present a detailed study about angular distribution ofγ-ray in space. The first, it is completed by MCNP4C program to simulate interaction between Neutron and sample. When the radioactive neutron source is area source and the shape of sample is coal ball with certain volume, characteristicγ-ray is received in the y-o-z plane. The research data will show the angular distribution of characteristic and give the flux maximum position of characteristicγ-ray, which is useful for finding the best detection position. Keeping the same distance between neutron source and sample, Change the sample radius to study the effect of the angular distribution ofγ-ray with the change of sample volume. In addition, this study reveals the differences of angular distribution ofγ-rays during the sample's shape change from ball to cube hexahedron. This paper briefly describes the main types of interaction between neutron and the materials. The development of Monte Carlo (Monte Carlo) methods and the main application of MCNP in research are also provided. The paper focuses on how to simulate the experiment by MCNP program to identify the spatial distribution ofγ-rays and to process the simulation results. Simulation results show that reflection method is better than receiving transmission method for receiving the promptγ-ray induced by neutron. Reference to the positive direction of z axis that is also the direction from neutron source to sample, maximum position ofγ-ray flux appears on the 0°angle, and distribution curves of different elements rapidly decline from 0°to 180°including C, H and O. With the radius of sample increasing, distribution curves of C and O respectively appear focus at 50°that means the smaller radius of the sample the more favorable for Transmission reception method and the bigger samples are good for reflection method. It can be seen that the spherical radius of sample favorable for the transmission-type reception method is 25cm in distribution curve of the H element. The results also show that the angular distribution ofγ-ray of the cube hexahedron sample and spherical sample with considerable volume meet the same rule. This study expands the applications of MCNP program in the simulation of particle transporting problems and the result also provides guidance for NIPGA experiments.