We performed a time-resolved spectroscopic study of the VUV/UV scintillation of gaseous argon as a function of pressure and electric field, by means of a wavelength sensitive detector operated with ...different radioactive sources. Our work conveys new evidence of distinctive features of the argon light which are in contrast with the general assumption that, for particle detection purposes, the scintillation can be considered to be largely monochromatic at 128 nm (second continuum). The wavelength and time-resolved analysis of the photon emission reveal that the dominant component of the argon scintillation during the first tens of ns is in the range 160, 325 nm. This light is consistent with the third continuum emission from highly charged argon ions/molecules. This component of the scintillation is field-independent up to 25 V/cm/bar and shows a very mild dependence with pressure in the range 1, 16 bar. The dynamics of the second continuum emission is dominated by the excimer formation time, whose variation as a function of pressure has been measured. Additionally, the time and pressure-dependent features of electron-ion recombination, in the second continuum band, have been measured. This study opens new paths toward a novel particle identification technique based on the spectral information of the noble-elements scintillation light.
We present a systematic study of the time and band-resolved scintillation in xenon-based time projection chambers (TPCs), performed simultaneously for the primary (S1) and secondary (S2) components ...in a small, purity-controlled, setup. We explore a range of conditions of general academic interest, focusing on those of relevance to contemporary TPCs: pressure range 1–10 bar, pressure-reduced electric fields of 0–100 V/cm/bar in the drift region (S1) and up to the proportional scintillation regime in the multiplication region (S2), and wavelength bands 145–250/250–400/400–600 nm, for both
α
and
β
particles. Attention is paid to the possibility of non-conventional scintillation mechanisms such as the 3rd continuum emission, recombination light from
β
-electrons at high pressure (for S1), emission from high-lying excited states and neutral bremsstrahlung (for S2). Time constants and, specially, scintillation yields have been obtained as a function of electric field and pressure, the latter aided by Geant4 simulations.
We report results of a search for light (≲10 GeV) particle dark matter with the XENON10 detector. The event trigger was sensitive to a single electron, with the analysis threshold of 5 electrons ...corresponding to 1.4 keV nuclear recoil energy. Considering spin-independent dark matter-nucleon scattering, we exclude cross sections σ(n)>7×10(-42) cm(2), for a dark matter particle mass m(χ)=7 GeV. We find that our data strongly constrain recent elastic dark matter interpretations of excess low-energy events observed by CoGeNT and CRESST-II, as well as the DAMA annual modulation signal.
We report on the thermal neutron flux measurements carried out at the Laboratorio Subterráneo de Canfranc (LSC) with two commercial
2
″
×
2
″
CLYC detectors. The measurements were performed as part ...of an experimental campaign at LSC with
3
He detectors, for establishing the sensitivity limits and use of CLYCs in low background conditions. A careful characterization of the intrinsic
α
and
γ
-ray background in the detectors was required and done with dedicated measurements. It was found that the
α
activities in the two CLYC crystals differ by a factor of three, and the use of Monte Carlo simulations and a Bayesian unfolding method allowed us to determine the specific
α
activities from the
238
U and
232
Th decay chains. The simulations and unfolding also revealed that the
γ
-ray background registered in the detectors is dominated by the intrinsic activity of the components of the detector such as the aluminum housing and photo-multiplier and that the activity within the crystal is low in comparison. The data from the neutron flux measurements with the two detectors were analyzed with different methodologies: one based on an innovative
α
/neutron pulse shape discrimination method and one based on the subtraction of the intrinsic
α
background that masks the neutron signals in the region of interest. The neutron sensitivity of the CLYCs was calculated by Monte Carlo simulations with MCNP6 and GEANT4. The resulting thermal neutron fluxes are in good agreement with complementary flux measurement performed with
3
He detectors, but close to the detection limit imposed by the intrinsic
α
activity.
Dark matter with Planck-scale mass (≃10^{19} GeV/c^{2}) arises in well-motivated theories and could be produced by several cosmological mechanisms. A search for multiscatter signals from ...supermassive dark matter was performed with a blind analysis of data collected over a 813 d live time with DEAP-3600, a 3.3 t single-phase liquid argon-based detector at SNOLAB. No candidate signals were observed, leading to the first direct detection constraints on Planck-scale mass dark matter. Leading limits constrain dark matter masses between 8.3×10^{6} and 1.2×10^{19} GeV/c^{2}, and ^{40}Ar-scattering cross sections between 1.0×10^{-23} and 2.4×10^{-18} cm^{2}. These results are interpreted as constraints on composite dark matter models with two different nucleon-to-nuclear cross section scalings.
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.
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