Design and construction of a new detector to measure ultra-low radioactive-isotope contamination of argon

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, ${}^{39}$Ar, a $\beta$ emitter of cosmogenic origin. For large detectors, the atmospheric ${}^{39}$Ar activity poses pile-up concerns. The use of argon extracted from underground wells, deprived of ${}^{39}$Ar, 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 ${}^{39}$Ar with respect to AAr by a factor larger than 1400. Assessing the ${}^{39}$Ar 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 $\gamma$-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.

13 pages, 8 figures. Corresponding author: E. Sánchez García

References in corpus (3)

• First Results from the DarkSide-50 Dark Matter Experiment at Laboratori Nazionali del Gran Sasso
• A Model of Nuclear Recoil Scintillation Efficiency in Noble Liquids
• Simulation of argon response and light detection in the DarkSide-50 dual phase TPC

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• A practical approach of high precision U and Th concentration measurement in acrylic
• The DarkSide-20k experiment
• Improving the light collection efficiency of silicon photomultipliers through the use of metalenses
• Study of cosmogenic activation above ground for the DarkSide-20k experiment
• Double Beta Decay Experiments at Canfranc Underground Laboratory
• FAT-GEMs: (Field Assisted) Transparent Gaseous-Electroluminescence Multipliers
• Optimised neutron yield calculations from ($\alpha ,n$) reactions with the modified SOURCES4 code
• Study of cosmogenic activation above ground of Ar for DarkSide-20k
• Development & Characterization of Electrodes for large-scale Xenon Time Projection Chambers
• Performance of the ReD TPC, a novel double-phase LAr detector with Silicon Photomultiplier Readout