ASTREA: Accelerator mass spectrometry Survey of Trace Radionuclides for Experiments in Astroparticle physics

在过去的三十年里，实验粒子物理学的巨大进步使得在寻找无中微子双β衰变和直接探测暗物质(DM)方面取得了强劲的进展。桌面仪器已成为数吨重的地下探测器，对极其罕见的相互作用具有极高的灵敏度。这一进展的关键是探测器中残留的天然放射性本底减少了许多数量级，这主要是通过在探测器建造之前和期间进行材料筛选实现的。建造这样的巨星所用的每一种材料和部件都必须经过彻底的分析，如果可能的话，还要进行优化，因为最轻微的自然放射性污染可能会压倒预期的信号，从而破坏实验的敏感性。许多技术进步以及地下安装都为过去和现在的实验的成功做出了贡献。但我们已经达到了材料筛选的要求，这通常是典型方法无法满足的。加速器质谱学(AMS)是其他领域的一项成熟技术，它为实现最终的灵敏度提供了希望的灯塔。AMS使用粒子加速器来提高灵敏度，并提供独特而突出的优势：-直接扫描导电材料；这比唯一的另一种直接方法-使用Ge探测器的伽马光谱分析-更好；-全分子背景抑制，这比常规的高灵敏度质谱学技术，如电感耦合等离子体质谱技术(ICPMS)更有优势。-使用气体电离探测器和高分辨率交替磁电扇区的单离子灵敏度，实现无噪声检测和一系列信号到背景的优化策略。-应用于中/短寿命同位素的筛选，例如用于现场电子和高压系统的各种塑料和其他绝缘体中的210Pb。在本请求中，我们考虑AMS材料筛选针对三个具体项目的贡献，这些项目具有加拿大的重大贡献和领导地位：Nexo、NEWS-G和DEAP/Darkside，这三个项目正在考虑在SNOLab运营，这是世界上最深和最干净的地下实验室之一。我们建议研究U和Th链的痕量放射性，测量铜、钛、丙烯酸和聚合物薄膜中的~(210)Pb和~(226)Ra的浓度。渥太华大学的A.E.Lalonde AMS(AEL-AMS)设施是加拿大唯一的AMS实验室，运行着一套3 mV的多元素AMS系统，专门设计用于灵敏而高效地测量像鳗系元素这样的大质量元素。AEL-AMS实施了样品制备化学实验室，配备了处理各种分析物原子和样品基质的设备，并受命开发新的应用程序以及促进此类分析所需的协议和技术基础设施。

In the last three decades, tremendous advances in experimental particle physics have enabled strong progression in the search for neutrinoless double beta decay (0?ßß) and the direct detection of dark matter (DM). Tabletop instruments have become multi-tonne underground detectors with excellent sensitivity to extremely rare interactions. Critical to this progress has been the reduction of residual natural radioactive backgrounds in the detectors by many orders of magnitude, accomplished mainly through material screening, before and during detector construction. Every material and component for building such giants has to be thoroughly analyzed and, if possible, optimized, as the slightest natural radioactive contamination can ruin the experiment's sensitivity by overwhelming the expected signal. Many technical advances, as well as underground installation have contributed to the success of past and current experiments. But we have reached material screening requirements that often cannot be met by typical methods. Accelerator Mass Spectrometry (AMS), an established technique in other fields, provides a beacon of hope to achieve the ultimate sensitivity. AMS uses a particle accelerator to enhance sensitivity and offer unique and outstanding advantages: - direct scanning of electrically conducting materials; this compares favourably with the only other direct method, gamma spectroscopy using a Ge detector, - total molecular background suppression, an advantage over regular high sensitivity mass spectrometry techniques like ICP-MS. - single ion sensitivity using gas ionization detectors and high resolution alternating magnetic and electric sectors, that enable noise-free detection and a series of signal to background optimization strategies. - application to screening for medium/short lifetime isotopes, e.g. 210Pb in a wide array of plastics and other insulators used for in-situ electronics and high voltage systems, In this request, we consider AMS material screening contributions targeted to three specific projects that have significant Canadian contributions and leadership: nEXO, NEWS-G and DEAP/DarkSide, and which are considering operating at SNOLab , one of the deepest and cleanest underground laboratories in the world. We propose to investigate the trace radioactivity due to U and Th chains, measure the concentration of 210Pb and 226Ra, in copper, titanium, acrylic and thin polymer films. The A. E. Lalonde AMS (AEL-AMS) facility at the University of Ottawa, the only AMS laboratory in Canada, operates a 3 MV, multi-element AMS system, specifically designed to sensitively and efficiently measure elements as massive as the actinides. AEL-AMS has implemented sample preparation chemistry labs equipped to handle a wide array of analyte atoms and sample matrices and has a mandate to develop new applications and the required protocols and technical infrastructure to facilitate such analyses.