DUSEL R&D: BetaCage: A Screener of Ultra-Low-Level Radioactive Surface Contamination

拟议中的深层地下科学与工程实验室（DUSEL）的一个重大承诺是为需要极低背景的实验提供屏蔽宇宙射线背景粒子的空间。这些实验旨在研究物理学的基本定律，例如我们对太阳如何发光的理解，中微子是否是自己的反粒子，以及弥漫在宇宙中的暗物质是什么。然而，为了充分利用对宇宙射线的屏蔽，这些实验必须用放射性水平很低的部件建造，即使是地球表面屏蔽场所现有的最好的屏蔽设施也不够灵敏。必须在地下建造新的筛选设施，以使这些低背景实验取得成功。 该提案寻求资源，以建造一个探测器，这将是世界上最灵敏的放射性表面污染，如低能电子发射放射性同位素的筛选器。这个探测器被称为“BetaCage”，将由一个超低背景的多丝正比室组成，使用大气压下的氖。这种筛选器将用于稀有相互作用物理实验和痕量放射性计数应用。BetaCage将探测到足够低的电子速率，使SuperCDMS的150 kg级达到其对WIMP暗物质的设计灵敏度，而不会受到错误识别的低能电子的限制。BetaCage也将是筛选阿尔法粒子的理想选择，在暗物质搜索、太阳中微子实验和无中微子双β衰变实验以及硅芯片工业和其他科学领域都有重要应用，许多都是社会普遍感兴趣的。其他更广泛的影响将包括对科学家进行辐射探测技术和低本底技术方面的培训。

One of the great promises of the proposed Deep Underground Science and Engineering Laboratory (DUSEL) is to provide space shielded from cosmic-ray background particles for experiments that require extremely low backgrounds. These experiments seek to study the fundamental laws of physics, such as our understanding of how the sun shines, whether the neutrino is its own antiparticle, and what is the dark matter pervading the universe. However, to take full advantage of the shielding from cosmic rays, these experiments must be built from components with such low levels of radioactivity that even the best screening facilities available in shielded sites at the Earth's surface are insufficiently sensitive. New screening facilities must be built underground to allow these low-background experiments to succeed. This proposal seeks resources to build a detector that would be the world's most sensitive screener of radioactive surface contamination such as low-energy-electron emitting radioisotopes. This detector, dubbed the "BetaCage," will consist of an ultra-low-background multi-wire proportional chamber using neon gas at atmospheric pressure. This screener would have applications for rare-interaction physics experiments and trace radioactive counting applications. The BetaCage would detect electron rates low enough for the 150 kg stage of SuperCDMS to reach its design sensitivity for WIMP dark matter without being limited by misidentified low-energy electrons. The BetaCage would also be ideal for screening alphas, with important applications for dark matter searches, solar neutrino experiments, and neutrinoless double beta decay experiments, as well as for the Si-chip industry and for other scientific fields, many of general societal interest. Additional broader impacts will include the training of scientists in radiation-detection technologies and low-background techniques.