Analysis of some Earth, Moon and Mars samples in terms of gamma ray energy absorption buildup factors: Penetration depth, weight fraction of constituent elements and photon energy dependence

The Earth, Moon and Mars samples have been investigated in terms of gamma ray energy absorption buildup factors (EABF) depending on penetration depth, weight fraction of constituent elements and photon energy. The five parameter geometric progression (G-P) fitting approximation has been used to compute the buildup factors in the energy region 0.015-15 MeV up to a penetration depth of 40 mean free paths (mfp). The maximum values of EABF have been observed for the Earth, Mars and Moon samples at 0.2, 0.3 and 0.2 MeV, respectively. At the corresponding energies where maximum EABF occur, the Earth samples have the highest and the Mars samples have the lowest EABF values. There is no significant variation in EABF for the Earth, Moon and Mars samples beyond 1 MeV, hence the values of EABF remain constant with the variation in chemical composition for all the given materials. Finally, the buildup factors so obtained have been discussed in function of the penetration depth, weight fraction of constituent elements and photon energy. (C) 2010 Elsevier Ltd. All rights reserved.