48 research outputs found
Measurement of isotopic separation of argon with the prototype of the cryogenic distillation plant Aria for dark matter searches
The Aria cryogenic distillation plant, located in Sardinia, Italy, is a key component of the DarkSide-20k experimental program for WIMP dark matter searches at the INFN Laboratori Nazionali del Gran Sasso, Italy. Aria is designed to purify the argon, extracted from underground wells in Colorado, USA, and used as the DarkSide-20k target material, to detector-grade quality. In this paper, we report the first measurement of argon isotopic separation by distillation with the 26 m tall Aria prototype. We discuss the measurement of the operating parameters of the column and the observation of the simultaneous separation of the three stable argon isotopes: 36Ar , 38Ar , and 40Ar . We also provide a detailed comparison of the experimental results with commercial process simulation software. This measurement of isotopic separation of argon is a significant achievement for the project, building on the success of the initial demonstration of isotopic separation of nitrogen using the same equipment in 2019
Study on cosmogenic activation above ground for the DarkSide-20k project
The activation of materials due to the exposure to cosmic rays may become an
important background source for experiments investigating rare event phenomena.
DarkSide-20k is a direct detection experiment for galactic dark matter
particles, using a two-phase liquid argon time projection chamber filled with
49.7 tonnes (active mass) of Underground Argon (UAr) depleted in 39Ar. Here,
the cosmogenic activity of relevant long-lived radioisotopes induced in the
argon and other massive components of the set-up has been estimated; production
of 120 t of radiopure UAr is foreseen. The expected exposure above ground and
production rates, either measured or calculated, have been considered. From the
simulated counting rates in the detector due to cosmogenic isotopes, it is
concluded that activation in copper and stainless steel is not problematic.
Activation of titanium, considered in early designs but not used in the final
design, is discussed. The activity of 39Ar induced during extraction,
purification and transport on surface, in baseline conditions, is evaluated to
be 2.8% of the activity measured in UAr from the same source, and thus
considered acceptable. Other products in the UAr such as 37Ar and 3H are shown
to not be relevant due to short half-life and assumed purification methods
Directionality of nuclear recoils in a liquid argon time projection chamber
The direct search for dark matter in the form of weakly interacting massive
particles (WIMP) is performed by detecting nuclear recoils (NR) produced in a
target material from the WIMP elastic scattering. A promising experimental
strategy for direct dark matter search employs argon dual-phase time projection
chambers (TPC). One of the advantages of the TPC is the capability to detect
both the scintillation and charge signals produced by NRs. Furthermore, the
existence of a drift electric field in the TPC breaks the rotational symmetry:
the angle between the drift field and the momentum of the recoiling nucleus can
potentially affect the charge recombination probability in liquid argon and
then the relative balance between the two signal channels. This fact could make
the detector sensitive to the directionality of the WIMP-induced signal,
enabling unmistakable annual and daily modulation signatures for future
searches aiming for discovery. The Recoil Directionality (ReD) experiment was
designed to probe for such directional sensitivity. The TPC of ReD was
irradiated with neutrons at the INFN Laboratori Nazionali del Sud, and data
were taken with 72 keV NRs of known recoil directions. The direction-dependent
liquid argon charge recombination model by Cataudella et al. was adopted and a
likelihood statistical analysis was performed, which gave no indications of
significant dependence of the detector response to the recoil direction. The
aspect ratio R of the initial ionization cloud is estimated to be 1.037 +/-
0.027 and the upper limit is R < 1.072 with 90% confidence levelComment: 20 pages, 10 figures, submitted to Eur. Phys. J.
Sensitivity projections for a dual-phase argon TPC optimized for light dark matter searches through the ionization channel
Dark matter lighter than 10 GeV/c encompasses a promising range of
candidates. A conceptual design for a new detector, DarkSide-LowMass, is
presented, based on the DarkSide-50 detector and progress toward DarkSide-20k,
optimized for a low-threshold electron-counting measurement. Sensitivity to
light dark matter is explored for various potential energy thresholds and
background rates. These studies show that DarkSide-LowMass can achieve
sensitivity to light dark matter down to the solar neutrino floor for GeV-scale
masses and significant sensitivity down to 10 MeV/c considering the Migdal
effect or interactions with electrons. Requirements for optimizing the
detector's sensitivity are explored, as are potential sensitivity gains from
modeling and mitigating spurious electron backgrounds that may dominate the
signal at the lowest energies
SiPM-matrix readout of two-phase argon detectors using electroluminescence in the visible and near infrared range
Proportional electroluminescence (EL) in noble gases is used in two-phase detectors for dark matter searches to record (in the gas phase) the ionization signal induced by particle scattering in the liquid phase. The âstandardâ EL mechanism is considered to be due to noble gas excimer emission in the vacuum ultraviolet (VUV). In addition, there are two alternative mechanisms, producing light in the visible and near infrared (NIR) ranges. The first is due to bremsstrahlung of electrons scattered on neutral atoms (âneutral bremsstrahlungâ, NBrS). The second, responsible for electron avalanche scintillation in the NIR at higher electric fields, is due to transitions between excited atomic states. In this work, we have for the first time demonstrated two alternative techniques of the optical readout of two-phase argon detectors, in the visible and NIR range, using a silicon photomultiplier matrix and electroluminescence due to either neutral bremsstrahlung or avalanche scintillation. The amplitude yield and position resolution were measured for these readout techniques, which allowed to assess the detection threshold for electron and nuclear recoils in two-phase argon detectors for dark matter searches. To the best of our knowledge, this is the first practical application of the NBrS effect in detection science
Design and construction of a new detector to measure ultra-low radioactive-isotope contamination of argon
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 ÎČ 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 Îł-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
Sensitivity of future liquid argon dark matter search experiments to core-collapse supernova neutrinos
Future liquid-argon DarkSide-20k and Argo detectors, designed for direct dark matter search, will be sensitive also to core-collapse supernova neutrinos, via coherent elastic neutrino-nucleus scattering. This interaction channel is flavor-insensitive with a high-cross section, enabling for a high-statistics neutrino detection with target masses of âŒ50 t and âŒ360 t for DarkSide-20k and Argo respectively. Thanks to the low-energy threshold of âŒ0.5 keVnr achievable by exploiting the ionization channel, DarkSide-20k and Argo have the potential to discover supernova bursts throughout our galaxy and up to the Small Magellanic Cloud, respectively, assuming a 11-Mâ progenitor star. We report also on the sensitivity to the neutronization burst, whose electron neutrino flux is suppressed by oscillations when detected via charged current and elastic scattering. Finally, the accuracies in the reconstruction of the average and total neutrino energy in the different phases of the supernova burst, as well as its time profile, are also discussed, taking into account the expected background and the detector response
DarkSide-50 results and the future liquid argon dark matter program
DarkSide uses a dual-phase Liquid Argon Time Projection Chamber (TPC) to search for
WIMP dark matter. The paper will present the latest result on the search for low mass
(MWIMP < 20Gev=c2) and high mass (MWIMP > 100Gev=c2) WIMPs from the current experiment,
DarkSide-50, running since mid 2015 a 50-kg-active-mass TPC, filled with argon from an
underground source. The next stage of the DarkSide program will be a new generation experiment
involving a global collaboration from all the current Argon based experiments. DarkSide-20k, is
designed as a 20-tonne fiducial mass TPC with SiPM based photosensors, expected to be free of
any background for an exposure of >100 ton x years. Like its predecessor DarkSide-20k will be
housed at the Gran Sasso (LNGS) underground laboratory, and it is expected to attain a WIMPnucleon
cross section exclusion sensitivity of 1047 cm2 for a WIMP mass of 1TeV=c2 in a 5 yr
run. A subsequent objective, towards the end of the next decade, will be the construction of the
ultimate detector, ARGO, with a 300 t fiducial mass to push the sensitivity to the neutrino floor
region for high mass WIMPs. The combination of the three experiments, part of a single family,
will cover completely the WIMP hypothesis from 1GeV=c2 to several hundreds of TeV=c2
masses