KDK: Potassium for Dark Matter

我们建议研究一种传统的核过程，它可能会揭穿一种有争议的说法，即探测到被认为构成宇宙大部分的奇异暗物质。在寻找暗物质的非常敏感的实验中，钾的放射性可能会贡献比之前认为的更多的背景。在其他方面，我们的项目需要一个相当于两根香蕉的放射源。 钾-40(40K)是一种天然存在的同位素。从其电子俘获衰变到Ar-40(40Ar)基态的低能X射线在各种罕见事件搜索中代表着重要的放射性背景，例如DAMA。然而，它的分支比从未被测量过，尽管它对于解释DAMA长期以来但有争议的暗物质发现是至关重要的。测量这一分支率是KDK(钾衰变)实验的目标。KDK将涉及一个40K的放射源，一个小的X射线探测器，以及一个大的否决权，以标记伽马从竞争的电子俘获衰变到40Ar的激发态。在2017年8月之前进行这一测量和拆除橡树岭国家实验室(TN)的MTAS设施是一个绝佳的机会之窗，这一否决具有独特的高效率。因此，我们请求为40K源、X射线探测器、真空基础设施和循环冷却器提供资金。这里要求的项目，特别是X射线探测器，以及对数据的分析，将构成硕士论文的大部分工作，也将被一名本科生暑期学生使用。

We propose to investigate a conventional nuclear process that may debunk a controversial claim for detection of the exotic dark matter thought to make up most of the universe. The radioactivity of potassium could contribute more background than previously thought to the very sensitive experiments looking for dark matter. Among other things, our project requires a radioactive source equivalent to two bananas. Potassium-40 (40K) is a naturally-occurring isotope. Low-energy X-rays from its electron capture decay to the ground state of argon-40 (40Ar) represent a significant radioactive background in various rare-event searches such as DAMA. However, its branching ratio has never been measured, though it is critical to the interpretation of the longstanding, yet controversial, claim for dark matter discovery by DAMA. Measuring this branching ratio is the goal of the KDK (potassium decay) experiment. KDK will involve a 40K radioactive source, a small X-ray detector, and a large veto to tag the gammas from the competing electron-capture decay to the excited state of 40Ar. There is an excellent window of opportunity to carry out this measurement before August 2017 and the dismantling of the MTAS facility at Oak Ridge National Laboratory (TN), a veto with a uniquely high efficiency. We therefore request funds for the 40K source, the X-ray detector, vacuum infrastructure, and a circulating chiller. The items requested here, and the X-ray detector in particular, as well as the analysis of the data, will form the bulk of the work in a Master's dissertation, and will be used by an undergraduate summer student as well.