KDK: Potassium for Dark Matter

我们建议调查一个传统的核过程，可能揭穿一个有争议的说法，即探测到被认为构成宇宙大部分的奇异暗物质。钾的放射性可以为寻找暗物质的非常敏感的实验提供比以前认为的更多的背景。除其他外，我们的项目需要相当于两个香蕉的放射源。 钾-40（40 K）是一种天然存在的同位素。从氩-40（40 Ar）的电子俘获衰变到基态的低能X射线代表了各种稀有事件搜索（如DAMA）中的重要放射性背景。然而，它的分支比从未被测量过，尽管它对于解释DAMA长期存在但有争议的暗物质发现声明至关重要。测量这个分支比是KDK（钾衰变）实验的目标。KDK将涉及一个40 K放射源、一个小型X射线探测器和一个大型否决权，以标记从竞争电子捕获衰变到40 Ar激发态的伽马射线。在2017年8月和橡树岭国家实验室（TN）的MTAS设施拆除之前，有一个很好的机会进行这项测量，这是一个具有独特高效率的否决权。因此，我们要求为40 K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，以及数据分析，将形成硕士论文中的大部分工作，并将由本科暑期学生使用。

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.