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The specific activity of the$$\\beta $$β decay of$$^{39}$$39 Ar in atmospheric argon is measured using the DEAP-3600 detector. DEAP-3600, located 2 km underground at SNOLAB, uses a total of (3269 ± 24) kg of liquid argon distilled from the atmosphere to search for dark matter. This detector is well-suited to measure the decay of$$^{39}$$39 Ar owing to its very low background levels. This is achieved in two ways: it uses low background construction materials; and it uses pulse-shape discrimination to differentiate between nuclear recoils and electron recoils. With 167 live-days of data, the measured specific activity at the time of atmospheric extraction is (0.964 ± 0.001$$_\\textrm{stat}$$stat ± 0.024$$_\\textrm{sys}$$sys ) Bq/kg$$_\\textrm{atmAr}$$atmAr , which is consistent with results from other experiments. A cross-check analysis using different event selection criteria and a different statistical method confirms the result.

The specific activity of the β decay of 39 Ar in atmospheric argon is measured using the DEAP-3600 detector. DEAP-3600, located 2 km underground at SNOLAB, uses a total of (3269 ± 24) kg of liquid argon distilled from the atmosphere to search for dark matter. This detector is well-suited to measure the decay of 39 Ar owing to its very low background levels. This is achieved in two ways: it uses low background construction materials; and it uses pulse-shape discrimination to differentiate between nuclear recoils and electron recoils. With 167 live-days of data, the measured specific activity at the time of atmospheric extraction is (0.964 ± 0.001 stat ± 0.024 sys ) Bq/kg atmAr , which is consistent with results from other experiments. A cross-check analysis using different event selection criteria and a different statistical method confirms the result.

The half-life of 39 Ar is measured using the DEAP-3600 detector located 2 km underground at SNOLAB. Between 2016 and 2020, DEAP-3600 used a target mass of (3269 ± 24) kg of liquid argon distilled from the atmosphere in a direct-detection dark matter search. Such an argon mass also enables direct measurements of argon isotope properties. The decay of 39 Ar in DEAP-3600 is the dominant source of triggers by two orders of magnitude, ensuring high statistics and making DEAP-3600 well-suited for measuring this isotope’s half-life. Use of the pulse-shape discrimination technique in DEAP-3600 allows powerful discrimination between nuclear recoils and electron recoils, resulting in the selection of a clean sample of 39 Ar decays. Observing over a period of 3.4 years, the 39 Ar half-life is measured to be ( 302 ± 8 stat ± 6 sys ) years. This new direct measurement suggests that the half-life of 39 Ar is significantly longer than the accepted value, with potential implications for measurements using this isotope’s half-life as input.

The half-life of$$^{39}$$39 Ar is measured using the DEAP-3600 detector located 2 km underground at SNOLAB. Between 2016 and 2020, DEAP-3600 used a target mass of (3269 ± 24) kg of liquid argon distilled from the atmosphere in a direct-detection dark matter search. Such an argon mass also enables direct measurements of argon isotope properties. The decay of$$^{39}$$39 Ar in DEAP-3600 is the dominant source of triggers by two orders of magnitude, ensuring high statistics and making DEAP-3600 well-suited for measuring this isotope’s half-life. Use of the pulse-shape discrimination technique in DEAP-3600 allows powerful discrimination between nuclear recoils and electron recoils, resulting in the selection of a clean sample of$$^{39}$$39 Ar decays. Observing over a period of 3.4 years, the$$^{39}$$39 Ar half-life is measured to be$$(302 \\pm 8_\\textrm{stat} \\pm 6_\\textrm{sys})$$( 302 ± 8 stat ± 6 sys ) years. This new direct measurement suggests that the half-life of$$^{39}$$39 Ar is significantly longer than the accepted value, with potential implications for measurements using this isotope’s half-life as input.

The knowledge of scintillation quenching of α -particles plays a paramount role in understanding α -induced backgrounds and improving the sensitivity of liquid argon-based direct detection of dark matter experiments. We performed a relative measurement of scintillation quenching in the MeV energy region using radioactive isotopes ( 222 Rn, 218 Po and 214 Po isotopes) present in trace amounts in the DEAP-3600 detector and quantified the uncertainty of extrapolating the quenching factor to the low-energy region.

Different geometries lie behind different architectural styles. There is now an improving alternative to the Euclidean/Cartesian geometrical environment in which the design process has developed up to now. Computational geometry has developed enough to be seriously considered as a source for new shapes for architectural objects: parametric functions and control point curves are entering the architectural design world. NURBS modelling allows the design of architecture with surfaces and volumes that could not even be thought of before the application of a computing device to their geometry. This fact means a deep change in the epistemological charter of the whole design process itself: the geometrical immanence of a project becomes unreadable by human capabilities because the reference shapes no longer have abstract and easy-to-deal-with images (i.e. a parabola, a sphere, an ellipsoid, a cube), instead they are cryptically hidden into very complex volume aggregations that can be designed only if computational geometry is assumed into the shape definition process. Therefore, the architectural design procedure has a new step that I call \\“computational filtering”, that allows the making of an option between the two geometrical environments. Obviously they can be mixed too, but at the moment I think this can be thought of in the same way as a standard and well-known shape-balancing procedure

Abstract The half-life of$$^{39}$$39 Ar is measured using the DEAP-3600 detector located 2 km underground at SNOLAB. Between 2016 and 2020, DEAP-3600 used a target mass of (3269 ± 24) kg of liquid argon distilled from the atmosphere in a direct-detection dark matter search. Such an argon mass also enables direct measurements of argon isotope properties. The decay of$$^{39}$$39 Ar in DEAP-3600 is the dominant source of triggers by two orders of magnitude, ensuring high statistics and making DEAP-3600 well-suited for measuring this isotope’s half-life. Use of the pulse-shape discrimination technique in DEAP-3600 allows powerful discrimination between nuclear recoils and electron recoils, resulting in the selection of a clean sample of$$^{39}$$39 Ar decays. Observing over a period of 3.4 years, the$$^{39}$$39 Ar half-life is measured to be$$(302 \\pm 8_\\textrm{stat} \\pm 6_\\textrm{sys})$$( 302 ± 8 stat ± 6 sys ) years. This new direct measurement suggests that the half-life of$$^{39}$$39 Ar is significantly longer than the accepted value, with potential implications for measurements using this isotope’s half-life as input.

Abstract DarkSide-20k is a novel liquid argon dark matter detector currently under construction at the Laboratori Nazionali del Gran Sasso (LNGS) of the Istituto Nazionale di Fisica Nucleare (INFN) that will push the sensitivity for Weakly Interacting Massive Particle (WIMP) detection into the neutrino fog. The core of the apparatus is a dual-phase Time Projection Chamber (TPC), filled with 50 tonnes of low radioactivity underground argon (UAr) acting as the WIMP target. NUV-HD-cryo Silicon Photomultipliers (SiPM)s designed by Fondazione Bruno Kessler (FBK) (Trento, Italy) were selected as the photon sensors covering two10.5 \\text m²10.5 m 2 Optical Planes, one at each end of the TPC, and a total of5 \\text m²5 m 2 photosensitive surface for the liquid argon veto detectors. This paper describes the Quality Assurance and Quality Control (QA/QC) plan and procedures accompanying the production of FBK NUV-HD-cryo SiPM wafers manufactured by LFoundry s.r.l. (Avezzano, AQ, Italy). SiPM characteristics are measured at 77 K at the wafer level with a custom-designed probe station. As of March 2025, 1314 of the 1400 production wafers (94% of the total) for DarkSide-20k were tested. The wafer yield is93.2± 2.593.2 ± 2.5 %, which exceeds the 80% specification defined in the original DarkSide-20k production plan.

Abstract The specific activity of theβ β decay of³⁹39 Ar in atmospheric argon is measured using the DEAP-3600 detector. DEAP-3600, located 2 km underground at SNOLAB, uses a total of (3269 ± 24) kg of liquid argon distilled from the atmosphere to search for dark matter. This detector is well-suited to measure the decay of³⁹39 Ar owing to its very low background levels. This is achieved in two ways: it uses low background construction materials; and it uses pulse-shape discrimination to differentiate between nuclear recoils and electron recoils. With 167 live-days of data, the measured specific activity at the time of atmospheric extraction is (0.964 ± 0.001_(\\textrm{stat}{}{})stat ± 0.024_(\\textrm{sys}{}{})sys ) Bq/kg_(\\textrm{atmAr}{}{})atmAr , which is consistent with results from other experiments. A cross-check analysis using different event selection criteria and a different statistical method confirms the result.

In the DEAP-3600 dark matter search experiment, precise reconstruction of the positions of scattering events in liquid argon is key for background rejection and defining a fiducial volume that enhances dark matter candidate events identification. This paper describes three distinct position reconstruction algorithms employed by DEAP-3600, leveraging the spatial and temporal information provided by photomultipliers surrounding a spherical liquid argon vessel. Two of these methods are maximum-likelihood algorithms: the first uses the spatial distribution of detected photoelectrons, while the second incorporates timing information from the detected scintillation light. Additionally, a machine learning approach based on the pattern of photoelectron counts across the photomultipliers is explored.