Weatherburn H
Br J Radiol. 1984 Feb;57(674):163-6. doi: 10.1259/0007-1285-57-674-163.
In order to use an air-filled ionisation chamber for dosimetry of a photon or electron beam in a material, it is necessary to know the restricted (Spencer-Attix) mass stopping power ratio of the material, relative to air. A method is described in which a conversion factor, k, is derived by comparing unrestricted stopping power ratios of various materials (relative to air) with those for water (relative to air). Provided that the material does not differ too greatly in effective atomic number from that of water, this ratio is independent of energy and is a constant for any material both for unrestricted and restricted stopping powers. Values of k have been calculated for 31 materials and application of any one such factor to the restricted mass stopping power ratio of water relative to air allows the appropriate restricted mass stopping power of the material, relative to air, to be derived.
为了在一种材料中使用充气电离室对光子束或电子束进行剂量测定，有必要了解该材料相对于空气的受限（斯宾塞 - 阿蒂克斯）质量阻止本领比。本文描述了一种方法，通过比较各种材料（相对于空气）与水（相对于空气）的非受限阻止本领比来推导一个转换因子k。只要该材料的有效原子序数与水的有效原子序数相差不太大，这个比值就与能量无关，并且对于任何材料的非受限和受限阻止本领来说都是一个常数。已经计算了31种材料的k值，将任何一个这样的因子应用于水相对于空气的受限质量阻止本领比，就可以得出该材料相对于空气的相应受限质量阻止本领。
