The Study Of Influence Factors Of Gamma-ray Backscattering Spectrum With MCNP5

Many factors influence the backscattering spectrum of gamma ray, including the material composition, thickness of the scatter, incident ray energy and geometric arrangement and so on. And they seriously hindered the application of the method ofγ-ray backscatter principle in the field of measurement and analysis. For example, the radiation shielding, radiation absorbed, dose measurements and non-destructive testing which is limited to absorb medium in the industrial, agricultural, and medical industry. However, the introduction of these factors, which are all done through experiments, is very general and rarely at the present stage of books and literature.Due to the limitation of the experimental conditions, it is difficult to carry out a depth research, what’s more, the time spent and the cost is very high. In order to identify the relationship between the inverse scattering energy spectrum, the gamma ray, the composition and thickness of scattering body, source and the geometric arrangement of detector and other factors and promote the gamma energy spectrum technology further, based on the method of Monte Carlo simulation and MCNP5, under the different condition, gamma ray emitted by 137Cs、60Co gets through different thickness of paraffin wax and glass Al, Fe, Cu and Pb. These different changes can be used to study the influence factors of backscattering spectrum of gamma ray. The following is the main effect and significance.1) According to the experiment and simulation, when the scatterer is thinner,with the backscattering spectrum area reduced, atomic numbers of the twokinds of photons, released by the sample, are higher than 26. This shows thatthe simulation is accurate and feasible. It also suggests that atomic number,which makes backscattered peak area of scatterer reduce, is not the same assome teaching materials on introduction of 13.2) Through the simulation, with the increase of the thickness of the scatterer,when gamma energy spectrum of the backscattered peak area is reduced,theatomic number is 26. And the scatterer thickness of 137Cs、60Co source isrespectively 16 mm and 24 mm. This indicates that the thickness of thescatterer is the key factors between peak area and atomic number.3) The saturated thickness of the scatterer is not only related to the radioactivesource, but also related to the distance of the source and detector, and can notonly depends on the nature of the scatterer.4) When the distance between the scatterer and radioactive source reaches acertain value, the backscattered peak area is not change. But it is only relatedto the nature of the scatterer, and has nothing to do with the energy sourceand source meter distance.5) The distance between the detector and the source, and the distance betweenthe scatterer and radioactive source, both have influence on the backscatteredpeak area, so the two factors must be considered when backscatter isshielded.According to the study, the factors was systematically concluded, which affect the backscattered gamma rays spectrum and the inner link among these factors have impact on the backscattering spectrum, having achieved good achievements. The study on the application of the backscattered energy spectrum technology, radiation shielding and the design of thickness gauge plays a scientific guidance, reflecting that MCNP5 process simulation in this highly repetitive strictly limited condition has important practical value.