34 research outputs found
Study of cosmogenic activation above ground for the DarkSide-20k experiment
The activation of materials due to exposure to cosmic rays may become an important background source for experiments investigating rare event phenomena. DarkSide-20k, currently under construction at the Laboratori Nazionali del Gran Sasso, is a direct detection experiment for galactic dark matter particles, using a two-phase liquid-argon Time Projection Chamber (TPC) filled with 49.7 tonnes (active mass) of Underground Argon (UAr) depleted in 39Ar. Despite the outstanding capability of discriminating
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background in argon TPCs, this background must be considered because of induced dead time or accidental coincidences mimicking dark-matter signals and it is relevant for low-threshold electron-counting measurements. Here, the cosmogenic activity of relevant long-lived radioisotopes induced in the experiment has been estimated to set requirements and procedures during preparation of the experiment and to check that it is not dominant over primordial radioactivity; particular attention has been paid to the activation of the 120 t of UAr used in DarkSide-20k. Expected exposures above ground and production rates, either measured or calculated, have been considered in detail. 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. The activity of 39Ar induced during extraction, purification and transport on surface is evaluated to be 2.8% of the activity measured in UAr by DarkSide-50 experiment, which used the same underground source, and thus considered acceptable. Other isotopes in the UAr such as 37Ar and 3H are shown not to be relevant due to short half-life and assumed purification methods
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
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
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Atmospheric Radioxenon Measurements in North Las Vegas, NV
PNNL deployed the ARSA radioxenon measurement system in North Las Vegas for two weeks in February and March 2006 for the purpose of measuring the radioxenon background at a level of sensitivity much higher than previously done in the vicinity of the NTS. The measurements establish what might be expected if future measurements are taken at NTS itself. The measurements are also relevant to test site readiness. A second detector, the PEMS, built and operated by DRI, was deployed in conjunction with the ARSA and contained a PIC, aerosol collection filters, and meteorological sensors. Originally, measurements were also to be performed at Mercury, NV on the NTS, but these were canceled due to initial equipment problems with the ARSA detector. Some of the radioxenon measurements detected 133Xe at levels up to 3 mBq/m3. This concentration of radioxenon is consistent with the observation of low levels of radioxenon emanating from distance nuclear reactors. Previous measurements in areas of high nuclear reactor concentration have shown similar results, but the western US, in general, does not have many nuclear reactors. Measurements of the wind direction indicate that the air carrying the radioxenon came from south of the detector and not from the NTS
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 ∼50 t and ∼360 t for DarkSide-20k and Argo respectively. Thanks to the low-energy threshold of ∼0.5 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-M⊙ 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
Study of cosmogenic activation above ground for the DarkSide-20k experiment
The activation of materials due to exposure to cosmic rays may become an important background source for experiments investigating rare event phenomena. DarkSide-20k, currently under construction at the Laboratori Nazionali del Gran Sasso, is a direct detection experiment for galactic dark matter particles, using a two-phase liquid-argon Time Projection Chamber (TPC) filled with 49.7 tonnes (active mass) of Underground Argon (UAr) depleted in 39Ar. Despite the outstanding capability of discriminating γ/β background in argon TPCs, this background must be considered because of induced dead time or accidental coincidences mimicking dark-matter signals and it is relevant for low-threshold electron-counting measurements. Here, the cosmogenic activity of relevant long-lived radioisotopes induced in the experiment has been estimated to set requirements and procedures during preparation of the experiment and to check that it is not dominant over primordial radioactivity; particular attention has been paid to the activation of the 120 t of UAr used in DarkSide-20k. Expected exposures above ground and production rates, either measured or calculated, have been considered in detail. 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. The activity of 39Ar induced during extraction, purification and transport on surface is evaluated to be 2.8% of the activity measured in UAr by DarkSide-50 experiment, which used the same underground source, and thus considered acceptable. Other isotopes in the UAr such as 37Ar and 3H are shown not to be relevant due to short half-life and assumed purification methods