We report on several features in the energy spectrum from an ultralow-noise germanium detector operated deep underground. By implementing a new technique able to reject surface events, a number of ...cosmogenic peaks can be observed for the first time. We discuss an irreducible excess of bulklike events below 3 keV in ionization energy. These could be caused by unknown backgrounds, but also dark matter interactions consistent with DAMA/LIBRA. It is not yet possible to determine their origin. Improved constraints are placed on a cosmological origin for the DAMA/LIBRA effect.
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Abstract The Single Volume Scatter Camera (SVSC) Collaboration aims to develop portable neutron imaging systems for a variety of applications in nuclear non-proliferation. Conventional double-scatter ...neutron imagers are composed of several separate detector volumes organized in at least two planes. A neutron must scatter in two of these detector volumes for its initial trajectory to be reconstructed. As such, these systems typically have a large footprint and poor geometric efficiency. We report on the design and characterization of a prototype monolithic neutron scatter camera that is intended to significantly improve upon the geometrical shortcomings of conventional neutron cameras. The detector consists of a 50 mm×56 mm× 60 mm monolithic block of EJ-204 plastic scintillator instrumented on two faces with arrays of 64 Hamamatsu S13360-6075PE silicon photomultipliers (SiPMs). The electronic crosstalk is limited to < 5% between adjacent channels and < 0.1% between all other channel pairs. SiPMs introduce a significantly elevated dark count rate over PMTs, as well as correlated noise from after-pulsing and optical crosstalk. In this article, we characterize the dark count rate and optical crosstalk and present a modified event reconstruction likelihood function that accounts for them. We find that the average dark count rate per SiPM is 4.3 MHz with a standard deviation of 1.5 MHz among devices. The analysis method we employ to measure internal optical crosstalk also naturally yields the mean and width of the single-electron pulse height. We calculate separate contributions to the width of the single-electron pulse-height from electronic noise and avalanche fluctuations. We demonstrate a timing resolution for a single-photon pulse to be (128 ± 4) ps. Finally, coincidence analysis is employed to measure external (pixel-to-pixel) optical crosstalk. We present a map of the average external crosstalk probability between 2×4 groups of SiPMs, as well as the in-situ timing characteristics extracted from the coincidence analysis. Further work is needed to characterize the performance of the camera at reconstructing single- and double-site interactions, as well as image reconstruction.
Above-ground antineutrino detection for nuclear reactor monitoring Sweany, M.; Brennan, J.; Cabrera-Palmer, B. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2015, Volume:
769
Journal Article
Peer reviewed
Open access
Antineutrino monitoring of nuclear reactors has been demonstrated many times (Klimov et al., 1994 1; Bowden et al., 2009 2; Oguri et al., 2014 3), however the technique has not as of yet been ...developed into a useful capability for treaty verification purposes. The most notable drawback is the current requirement that detectors be deployed underground, with at least several meters-water-equivalent of shielding from cosmic radiation. In addition, the deployment of liquid-based detection media presents a challenge in reactor facilities. We are currently developing a detector system that has the potential to operate above ground and circumvent deployment problems associated with a liquid detection media: the system is composed of segments of plastic scintillator surrounded by 6LiF/ZnS:Ag. ZnS:Ag is a radio-luminescent phosphor used to detect the neutron capture products of 6Li. Because of its long decay time compared to standard plastic scintillators, pulse-shape discrimination can be used to distinguish positron and neutron interactions resulting from the inverse beta decay (IBD) of antineutrinos within the detector volume, reducing both accidental and correlated backgrounds. Segmentation further reduces backgrounds by identifying the positron׳s annihilation gammas, a signature that is absent for most correlated and uncorrelated backgrounds. This work explores different configurations in order to maximize the size of the detector segments without reducing the intrinsic neutron detection efficiency. We believe that this technology will ultimately be applicable to potential safeguards scenarios such as those recently described by Huber et al. (2014) 4,5.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Development of an advanced antineutrino detector for reactor monitoring Classen, T.; Bernstein, A.; Bowden, N.S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2015, Volume:
771, Issue:
C
Journal Article
Peer reviewed
Open access
Here we present the development of a compact antineutrino detector for the purpose of nuclear reactor monitoring, improving upon a previously successful design. This paper will describe the design ...improvements of the detector which increases the antineutrino detection efficiency threefold over the previous effort. There are two main design improvements over previous generations of detectors for nuclear reactor monitoring: dual-ended optical readout and single volume detection mass. The dual-ended optical readout eliminates the need for fiducialization and increases the uniformity of the detector׳s optical response. The containment of the detection mass in a single active volume provides more target mass per detector footprint, a key design criteria for operating within a nuclear power plant. This technology could allow for real-time monitoring of the evolution of a nuclear reactor core, independent of reactor operator declarations of fuel inventories, and may be of interest to the safeguards community.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The COHERENT experiment is well poised to test sub-GeV dark matter models using detectors sensitive to coherent elastic neutrino-nucleus scattering (CEvNS) in the π+ decay-at-rest (π-DAR) neutrino ...beam produced by the Spallation Neutron Source. We show a planned 750-kg single-phase liquid argon scintillation detector would place leading limits on scalar light dark matter models for dark matter particles produced through vector and leptophobic portals in the absence of other effects beyond the standard model. The characteristic timing profile of a π-DAR beam allows a unique opportunity for constraining systematic uncertainties on the standard model background using a time window where dark matter signal is not expected, enhancing expected sensitivity. Additionally, we discuss future prospects which show that an on-axis CEvNS detector would probe the thermal abundance for a scalar dark matter candidate for all couplings α′ ≤ 1 for 15 MeV dark matter with just 1.0 tonne-yr of exposure with increased exposure testing a wider range of dark matter masses and spins.
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OBJECTIVESA culture-of-safety survey of our hospital staff revealed fear-based reluctance to question those in authority. We aimed to examine provider approachability (words and actions that promote ...trust and reduce or eliminate fear of interaction).
METHODSProviders and staff completed an anonymous facility-wide survey (survey 1) regarding perceptions of provider approachability. Results were safely communicated to providers, and improvement resources were offered. A follow-up survey (survey 2 S2) was performed.
RESULTSThe survey participation rate was 59% (389/658). Eighty-four percent of providers had improved scores in S2. Mean top-box scores improved from 0.63 to 0.76 (P < .001). Providers deemed less approachable by nonprovider staff were also deemed less approachable by their peers (r = 0.82; survey 1). Forty-four percent reported improvement in the safety culture in S2. Twenty-eight percent of providers reported making efforts to improve how they were perceived by others.
CONCLUSIONSProvider approachability surveys are a safe, effective method of assessing and encouraging positive interactions that promote trust and influence positive communication. The process created an opportunity to identify and assist providers who were less approachable.
The coherent elastic scattering of neutrinos off nuclei has eluded detection for four decades, even though its predicted cross section is by far the largest of all low-energy neutrino couplings. This ...mode of interaction offers new opportunities to study neutrino properties and leads to a miniaturization of detector size, with potential technological applications. We observed this process at a 6.7σ̃ confidence level, using a low-background, 14.6-kilogram CsINa scintillator exposed to the neutrino emissions from the Spallation Neutron Source at Oak Ridge National Laboratory. Characteristic signatures in energy and time, predicted by the standard model for this process, were observed in high signal-to-background conditions. Improved constraints on nonstandard neutrino interactions with quarks are derived from this initial data set.
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BFBNIB, NMLJ, NUK, ODKLJ, PNG, SAZU, UL, UM, UPUK
We report the first measurement of coherent elastic neutrino-nucleus scattering (CEvNS) on argon using a liquid argon detector at the Oak Ridge National Laboratory Spallation Neutron Source. Two ...independent analyses prefer CEvNS over the background-only null hypothesis with greater than 3σ significance. The measured cross section, averaged over the incident neutrino flux, is (2.2±0.7)×10^{-39} cm^{2}-consistent with the standard model prediction. The neutron-number dependence of this result, together with that from our previous measurement on CsI, confirms the existence of the CEvNS process and provides improved constraints on nonstandard neutrino interactions.
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