Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116, Braunschweig, Germany.
Appl Radiat Isot. 2021 Apr;170:109624. doi: 10.1016/j.apradiso.2021.109624. Epub 2021 Feb 1.
The triple-to-double coincidence ratio (TDCR) and the CIEMAT/NIST efficiency tracing (CNET) methods are important techniques for accurate activity determination in radionuclide metrology and other fields. The methods require liquid scintillation (LS) counters with three (TDCR) or two (CNET) photomultiplier tubes (PMTs), respectively, and the original techniques assume that the responses of all PMTs in a counter system are identical. This assumption is, however, often not fulfilled. This may have significant consequences for the activity determination, and dedicated corrections are required. Corresponding effects and possible corrections for the TDCR method were discussed in a recent article (Kossert et al., 2020) while the CNET method was not included in that work. The intention of this paper is to present a brief theoretical consideration of this problem. This paper makes clear that for most radionuclides potential PMT asymmetries in CNET counters are of minor importance. In addition, measures to identify potential asymmetries in these counters are discussed.
三重-双符合比（TDCR）和 CIEMAT/NIST 效率追踪（CNET）方法是放射性核素计量学和其他领域中准确确定活度的重要技术。这两种方法分别需要具有三个（TDCR）或两个（CNET）光电倍增管（PMT）的液体闪烁（LS）计数器，并且原始技术假设计数器系统中所有 PMT 的响应都是相同的。然而，这种假设通常不成立。这可能对活度确定有重大影响，需要进行专门的修正。Kossert 等人（2020 年）最近的一篇文章讨论了 TDCR 方法的相应影响和可能的修正，而该工作并未包括 CNET 方法。本文的目的是对这一问题进行简要的理论考虑。本文明确指出，对于大多数放射性核素，CNET 计数器中潜在的 PMT 不对称性的重要性较小。此外，还讨论了识别这些计数器中潜在不对称性的措施。
