A dedicated analysis of the muon-induced background in the EDELWEISS dark matter search has been performed on a data set acquired in 2009 and 2010. The total muon flux underground in the Laboratoire ...Souterrain de Modane (LSM) was measured to be Φμ=(5.4±0.2-0.9+0.5)muons/m2/d. The modular design of the μ-veto system allows the reconstruction of the muon trajectory and hence the determination of the angular dependent muon flux in LSM. The results are in good agreement with both MC simulations and earlier measurements. Synchronization of the μ-veto system with the phonon and ionization signals of the Ge detector array allowed identification of muon-induced events. Rates for all muon-induced events Γμ=(0.172±0.012)evts/(kgd) and of WIMP-like events Γμ–n=0.008-0.004+0.005evts/(kgd) were extracted. After vetoing, the remaining rate of accepted muon-induced neutrons in the EDELWEISS-II dark matter search was determined to be Γirredμ–n<6·10-4evts/(kgd) at 90% C.L. Based on these results, the muon-induced background expectation for an anticipated exposure of 3000kgd for EDELWEISS-III is N3000kgdμ–n<0.6 events.
A backing detector for order-keV neutrons Biekert, A.; Chaplinsky, L.; Fink, C.W. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2022, Letnik:
1039
Journal Article
Recenzirano
Odprti dostop
We have designed and tested a large-area (0.15 m2) neutron detector based on neutron capture on 6Li. The neutron detector design has been optimized for the purpose of tagging the scattering angle of ...keV-scale neutrons. These neutron detectors would be employed to calibrate the low-energy (<100 eV) nuclear recoil in detectors for dark matter and coherent elastic neutrino nucleus scattering (CEνNS). We describe the design, construction, and characterization of a prototype. The prototype is designed to have a tagging efficiency of ∼25% at the relevant O(keV) neutron energies, and with a mean capture time of ∼17μs. The prototype was characterized using a 252Cf neutron source and agreement with the simulation was observed within a few percent level.
A backing detector for order-keV neutrons Biekert, A.; Chaplinsky, L.; Fink, C. W. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2022, Letnik:
1039
Journal Article
Recenzirano
Odprti dostop
In this work, we have designed and tested a large-area (0.15 m2) neutron detector based on neutron capture on 6Li. The neutron detector design has been optimized for the purpose of tagging the ...scattering angle of keV-scale neutrons. These neutron detectors would be employed to calibrate the low-energy (<100 eV) nuclear recoil in detectors for dark matter and coherent elastic neutrino nucleus scattering (CE$\textit{v}$NS). We describe the design, construction, and characterization of a prototype. The prototype is designed to have a tagging efficiency of ~25% at the relevant $\mathcal{O}$(keV) neutron energies, and with a mean capture time of ~ 17 μs. The prototype was characterized using a 252Cf neutron source and agreement with the simulation was observed within a few percent level.
We present a measurement of the cosmogenic activation in the cryogenic germanium detectors of the EDELWEISS III direct dark matter search experiment. The decay rates measured in detectors with ...different exposures to cosmic rays above ground are converted into production rates of different isotopes. The measured production rates in units of nuclei/kg/day are 82 ± 21 for 3H, 2.8 ± 0.6 for 49V, 4.6 ± 0.7 for 55Fe, and 106 ± 13 for 65Zn. These results are the most accurate for these isotopes. A 90% C.L. lower limit on the production rate of 68Ge of 71 nuclei/kg/day is also presented. They are compared to model predictions present in literature and to estimates calculated with the ACTIVIA code.
The EDELWEISS-II collaboration has completed a direct search for WIMP dark matter using cryogenic Ge detectors (400g each) and 384kg×days of effective exposure. A cross-section of 4.4×10-8pb is ...excluded at 90% C. L. for a WIMP mass of 85GeV. The next phase, EDELWEISS-III, aims to probe spin-independent WIMP-nucleon cross-sections down to a few ×10-9pb. We present here the study of gamma and neutron background coming from radioactive decays in the set-up and shielding materials. We have carried out Monte Carlo simulations for the completed EDELWEISS-II setup with GEANT4 and normalised the expected background rates to the measured radioactivity levels (or their upper limits) of all materials and components. The expected gamma-ray event rate in EDELWEISS-II at 20–200keV agrees with the observed rate of 82 events/kg/day within the uncertainties in the measured concentrations. The calculated neutron rate from radioactivity of 1.0–3.1 events (90% C. L.) at 20–200keV in the EDELWEISS-II data together with the expected upper limit on the misidentified gamma-ray events (⩽0.9), surface betas (⩽0.3), and muon-induced neutrons (⩽0.7), do not contradict five observed events in nuclear recoil band. We have then extended the simulation framework to the EDELWEISS-III configuration with 800g crystals, better material purity and additional neutron shielding inside the cryostat. The gamma-ray and neutron backgrounds in 24kg fiducial mass of EDELWEISS-III have been calculated as 14–44 events/kg/day and 0.7–1.4 events per year, respectively. The results of the background studies performed in the present work have helped to select better purity components and improve shielding in EDELWEISS-III to further reduce the expected rate of background events in the next phase of the experiment.
We report on a search for low-energy (E < 20 keV) WIMP-induced nuclear recoils using data collected in 2009 - 2010 by EDELWEISS from four germanium detectors equipped with thermal sensors and an ...electrode design (ID) which allows to efficiently reject several sources of background. Using an exposure of 113 kg.d, we find no evidence for an exponential distribution of low-energy nuclear recoils that could be attributed to WIMP elastic scattering. For WIMPs of mass 10 GeV, the observation of one event in the WIMP search region results in a 90% CL limit of 1.0 \times 10^-5 pb on the spin-independent WIMP-nucleon scattering cross-section, which constrains the parameter space associated with the findings reported by the CoGeNT, DAMA and CRESST experiments.
We have designed and tested a large-area (0.15~m\(^2\)) neutron detector based on neutron capture on \ce{^{6}Li}. The neutron detector design has been optimized for the purpose of tagging the ...scattering angle of keV-scale neutrons. These neutron detectors would be employed to calibrate the low-energy (\(<\)100 eV) nuclear recoil in detectors for dark matter and coherent elastic neutrino nucleus scattering (CE\(\nu\)NS). We describe the design, construction, and characterization of a prototype. The prototype is designed to have a tagging efficiency of \(\sim\)25\% at the relevant \(\mathcal{O}\)(keV) neutron energies, and with a mean capture time of \(\sim\)17\(~\mu\)s. The prototype was characterized using a \ce{^{252}Cf} neutron source and agreement with the simulation was observed within a few percent level.
Scintillator doped with a high neutron-capture cross-section material can be used to detect neutrons via their resulting gamma rays. Examples of such detectors using liquid scintillator have been ...successfully used in high-energy physics experiments. However, a liquid scintillator can leak and is not as amenable to modular or complex shapes as a solid scintillator. Polystyrene-based scintillators from a variety of gadolinium compounds with varying concentrations were polymerized in our laboratory. The light output, emission spectra, and attenuation length of our samples were measured and light collection strategies using a wavelength shifting (WLS) fiber were evaluated. The measured optical parameters were used to tune a Geant4-based optical Monte Carlo, enabling the trapping efficiency to be calculated. This technology was also evaluated as a possible neutron veto for the direct detection dark matter experiment, Super Cryogenic Dark Matter Search (SuperCDMS).
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