This paper presents the results of research on photon reflection from plane targets based on Monte Carlo simulations performed by the MCNP code. Five materials (water, concrete, aluminum, iron, and copper) are examined in the area of initial photon energies of up to 200 keV. The values of the total number albedo for photons dependent on the initial photon energy or the mean number of photon scatterings are calculated and graphically presented. We have shown that the values of the total number albedo for different target materials, expressed as a function of the mean number of photon scatterings, are in good agreement with each other and can be approximated by simple, universal analytic functions obtained by the least squares method. The accuracy of these analytic appoximations is confirmed by their comparison with the results of PENELOPE and FOTELP Monte Carlo codes
This pa per pres ents the re sults of the anal y ses of pho ton re flec tion from pla nar tar gets for nor mal pho ton in ci dence and for dif fer ent shield ing ma te ri als (wa ter, con crete, alu mi num, iron, and cop per), in the range of the ini tial pho ton en er gies from 20 keV to 300 keV. Cal cu lations of pho ton re flec tion pa ram e ters based on the re sults of Monte Carlo sim u la tions of the pho ton trans port have been per formed us ing MCNP4C code. In te gral re flec tion co ef fi cients, pre sented as func tions of the ra tio of to tal cross-sec tion of pho tons and ef fec tive atomic number of tar get ma te rial, show uni ver sal be hav iour for all the ana lysed shield ing ma te ri als in the se lected en ergy do main.
The possibility of expressing the total particle and energy reflection coefficients of low-energy photons in the form of universal functions valid for different shielding materials is investigated in this paper. The analysis is based on the results of Monte Carlo simulations of photon reflection by using MCNP, FOTELP, and PENELOPE codes. The normal incidence of the narrow monoenergetic photon beam of the unit intensity and of initial energies from 20 keV up to 100 keV is considered, and particle and energy reflection coefficients from the plane homogenous targets of water, aluminum, and iron are determined and compared. The representations of albedo coefficients on the initial photon energy, on the probability of large-angle photon scattering, and on the mean number of photon scatterings are examined. It is found out that only the rescaled albedo coefficients dependent on the mean number of photon scatterings have the form of universal functions and these functions are determined by applying the least square method
In this paper we present the results of calculations and analyses of the
integral particle reflection coefficient of photons for oblique photon
incidence on planar targets, in the domain of initial photon energies from
100 keV to 300 keV. The results are based on the Monte Carlo simulations of
the photon reflection from water, concrete, aluminum, iron, and copper
materials, performed by the MCNP code. It has been observed that the integral
particle reflection coefficient as a function of the ratio of total
cross-section of photons and effective atomic number of target material shows
universal behavior for all the analyzed shielding materials in the selected
energy domain. Analytical formulas for different angles of photon incidence
have been proposed, which describe the reflection of photons for all the
materials and energies analyzed.
For the photon transport kernel in form of the Thomson scattering function and a restrictive photon diffusion directed only toward free surface, several exact expressions of back scattered fluxes are demonstrated. The solving approach was established on a lemma proved by Placzek combined with the Fourier analytic inversion technique or the order of scattering method. Albedo problem in case of the homogeneous plane shield of iron subjected to the photons normally incident on the free surface is treated. Comparison of the results obtained by the analytical and Monte Carlo methods for the reflection of 40 and 60 keV photons from iron target confirms the domination of the single scattered photon flux and the strong influence of the scattering function anisotropy in reflection process at low energies
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