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

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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.