Physics Department, Faculty of Science, University of Novi Sad, Novi Sad 21000, Serbia.
Med Phys. 2013 Aug;40(8):083902. doi: 10.1118/1.4812433.
The purpose of this study was to explore the effects of a paraffin screen located at various positions in the maze on the neutron dose equivalent at the maze door.
The neutron dose equivalent was measured at the maze door of a room containing a 15 MV linear accelerator for x-ray therapy. Measurements were performed for several positions of the paraffin screen covering only 27.5% of the cross-sectional area of the maze. The neutron dose equivalent was also measured at all screen positions. Two simple models of the neutron source were considered in which the first assumed that the source was the cross-sectional area at the inner entrance of the maze, radiating neutrons in an isotropic manner. In the second model the reduction in the neutron dose equivalent at the maze door due to the paraffin screen was considered to be a function of the mean values of the neutron fluence and energy at the screen.
The results of this study indicate that the equivalent dose at the maze door was reduced by a factor of 3 through the use of a paraffin screen that was placed inside the maze. It was also determined that the contributions to the dosage from areas that were not covered by the paraffin screen as viewed from the dosimeter, were 2.5 times higher than the contributions from the covered areas. This study also concluded that the contributions of the maze walls, ceiling, and floor to the total neutron dose equivalent were an order of magnitude lower than those from the surface at the far end of the maze.
This study demonstrated that a paraffin screen could be used to reduce the neutron dose equivalent at the maze door by a factor of 3. This paper also found that the reduction of the neutron dose equivalent was a linear function of the area covered by the maze screen and that the decrease in the dose at the maze door could be modeled as an exponential function of the product φ·E at the screen.
本研究旨在探讨迷宫不同位置的石蜡屏蔽对迷宫门口中子剂量当量的影响。
在含有用于 X 射线治疗的 15MV 直线加速器的房间内，对迷宫门口的中子剂量当量进行了测量。对仅覆盖迷宫横截面积 27.5%的石蜡屏蔽的几个位置进行了测量。还在所有屏蔽位置测量了中子剂量当量。在这两个模型中，考虑了两种简单的中子源模型。在第一个模型中，假设源是迷宫内入口的横截面，以各向同性的方式辐射中子。在第二个模型中，由于石蜡屏蔽，迷宫门口的中子剂量当量的减少被认为是屏蔽处中子注量和能量的平均值的函数。
本研究结果表明，通过在迷宫内部放置石蜡屏蔽，可将迷宫门口的当量剂量降低 3 倍。还确定了，从剂量计角度来看，未被石蜡屏蔽覆盖的区域的剂量贡献比被覆盖区域的剂量贡献高 2.5 倍。本研究还得出结论，迷宫墙壁、天花板和地板对总中子剂量当量的贡献比迷宫末端表面的贡献低一个数量级。
本研究表明，石蜡屏蔽可将迷宫门口的中子剂量当量降低 3 倍。本文还发现，中子剂量当量的减少是迷宫屏蔽面积的线性函数，并且迷宫门口剂量的减少可以用屏蔽处φ·E 的乘积建模为指数函数。
