Cassette P, Ahn G H, Alzitzoglou T, Aubineau-Lanièce I, Bochud F, Garcia Torano E, Grau Carles A, Grau Malonda A, Kossert K, Lee K B, Laedermann J P, Simpson B R S, van Wyngaardt W M, Zimmerman B E
LNE-LNHB, 91191 Gif sur Yvette cedex, France.
Appl Radiat Isot. 2006 Oct-Nov;64(10-11):1471-80. doi: 10.1016/j.apradiso.2006.02.080. Epub 2006 Apr 5.
The CIEMAT/NIST and TDCR methods in liquid scintillation counting, initially developed for the activity standardization of pure-beta radionuclides, have been extended to the standardization of electron capture and beta-gamma radionuclides. Both methods require the calculation of the energy spectrum absorbed by the liquid scintillator. For radionuclides emitting X-rays or gamma-rays, when the energy is greater than a few tens of keV the Compton interaction is important and the absorption is not total. In this case, the spectrum absorbed by the scintillator must be calculated using analytical or stochastic models. An illustration of this problem is the standardization of 54Mn, which is a radionuclide decaying by electron capture. The gamma transition, very weakly converted, leads to the emission of an 835 keV photon. The calculation of the detection efficiency of this radionuclide requires the calculation of the energy spectrum transferred to the scintillator after the absorption of the gamma ray and the associated probability of absorption. The validity of the method is thus dependent on the correct calculation of the energy transferred to the scintillator. In order to compare the calculation results obtained using various calculation tools, and to provide the metrology community with some information on the choice of these tools, the LS working group of the ICRM organised a comparison of the calculated absorbed spectra for the 835 keV photon of 54Mn. The result is the spectrum of the energy absorbed by the scintillator per emission of an 835 keV gamma ray. This exercise was proposed for a standard 20 ml LS glass vial and for LS cocktail volumes of 10 and 15 ml. The calculation was done for two different cocktails: toluene and a widely used commercial cocktail, Ultima Gold. The paper describes the results obtained by nine participants using a total of 12 calculation codes.
液体闪烁计数中的CIEMAT/NIST和TDCR方法最初是为纯β放射性核素的活度标准化而开发的，现已扩展到电子俘获和β-γ放射性核素的标准化。这两种方法都需要计算液体闪烁体吸收的能谱。对于发射X射线或γ射线的放射性核素，当能量大于几十keV时，康普顿相互作用很重要，吸收并不完全。在这种情况下，必须使用解析模型或随机模型来计算闪烁体吸收的能谱。这个问题的一个例子是54Mn的标准化，它是一种通过电子俘获衰变的放射性核素。γ跃迁的内转换非常弱，会发射出835 keV的光子。计算这种放射性核素的探测效率需要计算γ射线吸收后转移到闪烁体的能谱以及相关的吸收概率。因此，该方法的有效性取决于转移到闪烁体的能量的正确计算。为了比较使用各种计算工具获得的计算结果，并为计量学界提供有关这些工具选择的一些信息，ICRM的LS工作组组织了一次对54Mn的835 keV光子计算吸收能谱的比较。结果是每次发射835 keVγ射线时闪烁体吸收的能量谱。这项工作针对一个标准的20 ml LS玻璃瓶以及10 ml和15 ml的LS鸡尾酒体积进行。计算针对两种不同的鸡尾酒进行：甲苯和一种广泛使用的商业鸡尾酒Ultima Gold。本文描述了九名参与者使用总共12种计算代码获得的结果。
