Abstract
Large liquid argon detectors offer one of the best avenues for the detection of galactic weakly interacting massive particles (WIMPs) via their scattering on atomic nuclei. The liquid argon target allows exquisite discrimination between nuclear and electron recoil signals via pulse-shape discrimination of the scintillation signals. Atmospheric argon (AAr), however, has a naturally occurring radioactive isotope, 39Ar, a β emitter of cosmogenic origin. For large detectors, the atmospheric 39Ar activity poses pile-up concerns. The use of argon extracted from underground wells, deprived of 39Ar, is key to the physics potential of these experiments. The DarkSide-20k dark matter search experiment will operate a dual-phase time projection chamber with 50 tonnes of radio-pure underground argon (UAr), that was shown to be depleted of 39Ar with respect to AAr by a factor larger than 1400. Assessing the 39Ar content of the UAr during extraction is crucial for the success of DarkSide-20k, as well as for future experiments of the Global Argon Dark Matter Collaboration (GADMC). This will be carried out by the DArT in ArDM experiment, a small chamber made with extremely radio-pure materials that will be placed at the centre of the ArDM detector, in the Canfranc Underground Laboratory (LSC) in Spain. The ArDM LAr volume acts as an active veto for background radioactivity, mostly γ-rays from the ArDM detector materials and the surrounding rock. This article describes the DArT in ArDM project, including the chamber design and construction, and reviews the background required to achieve the expected performance of the detector.
Highlights
20133, Italy 47Interuniversity Consortium for Science and Technology of Materials, Firenze 50121, Italy 48Saint Petersburg Nuclear Physics Institute, Gatchina 188350, Russia 49Physics Department, Princeton University, Princeton, NJ 08544, USA 50Department of Physics, Engineering Physics and Astronomy, Queen’s University, Kingston, ON K7L 3N6, Canada 51National Research Centre Kurchatov Institute, Moscow 123182, Russia 52Amherst Center for Fundamental Interactions and Physics Department, University of Massachusetts, Amherst, MA 01003, USA 53National Institute for R&D of Isotopic and Molecular Technologies, Cluj-Napoca, 400293, Romania 54Joint Institute for Nuclear Research, Dubna 141980, Russia 55INFN Laboratori Nazionali di Frascati, Frascati 00044, Italy 56APC, Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Obs de Paris, USPC, Paris 75205, France 57Department of Chemistry, University of Crete, P.O
The DarkSide-20k dark matter search experiment will operate a dual-phase time projection chamber with 50 tonnes of radio-pure underground argon (UAr), that was shown to be depleted of 39Ar with respect to Atmospheric argon (AAr) by a factor larger than 1400
Single- or dual-phase LAr TPC with pulse-shape discrimination provides excellent sensitivity to weakly interacting massive particles (WIMPs) masses above ∼30 GeV/c2
Summary
The DArT in ArDM experiment at LSC aims at measuring UAr-to-AAr 39Ar depletion factors of the order of 1000 with 10% precision in one week of running. Two dedicated boards attached to the bottom and top acrylic disk with acrylic screws hold the SiPMs. Currently in its construction phase, the DArT in ArDM experiment is expected to test UAr for DarkSide-20k, and for any future experiment of the GADMC, such as ARGO [12] and a possible tonne-scale detector to search for light dark matter. In its construction phase, the DArT in ArDM experiment is expected to test UAr for DarkSide-20k, and for any future experiment of the GADMC, such as ARGO [12] and a possible tonne-scale detector to search for light dark matter It is being considered for use by other experiments [13]
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