Effect of medium size on the γ-ray buildup factor for energy absorption in water
LI Hua1,2, ZHAO Yuan2, LIU Liye2, XIAO Yunshi2, LI Junli1
1. Key Laboratory of High Energy Radiation Imaging Fundamental Science, Key Laboratory of Particle and Radiation Imaging ofMinistry of Education, Department of Engineering Physics, Tsinghua University, Beijing 100084, China;
2. Radiation Dosimetry Laboratory, Department of Health Physics, China Institute for Radiation Protection, Taiyuan 030006, China
Abstract：γ-Ray buildup factors calculated using an infinite medium model can differ greatly for actual finite models. The precision of the buildup factors used in the actual calculations is improved using Monte Carlo simulations to study the variation of the energy absorption buildup factors as a function of the medium size for water using a cylindrical model. The results show that as the cylinder radius increases, the buildup factors in water first increase up to a maximum. The corresponding radius values for the maximum buildup factors are not influenced by the γ-ray energy or the medium thickness, but are only related to the distance from the point source to the measured point on the medium surface. The differences between the buildup factors as the cylinder radius increases are larger than for the maximums, and the variation is linear for some mean free paths. As the medium thickness increases, the corresponding range of the mean free paths where the variation is linear also increases. This work provides a reference for analyzing calculational errors in shielding designs.
李华, 赵原, 刘立业, 肖运实, 李君利. 介质尺寸对水中γ射线吸收剂量累积因子的影响[J]. 清华大学学报（自然科学版）, 2017, 57(5): 525-529.
LI Hua, ZHAO Yuan, LIU Liye, XIAO Yunshi, LI Junli. Effect of medium size on the γ-ray buildup factor for energy absorption in water. Journal of Tsinghua University(Science and Technology), 2017, 57(5): 525-529.
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2017, Vol. 57 
