[Show abstract][Hide abstract] ABSTRACT: The COHERENT collaboration's primary objective is to measure coherent elastic
neutrino-nucleus scattering (CEvNS) using the unique, high-quality source of
tens-of-MeV neutrinos provided by the Spallation Neutron Source (SNS) at Oak
Ridge National Laboratory (ORNL). In spite of its large cross section, the
CEvNS process has never been observed, due to tiny energies of the resulting
nuclear recoils which are out of reach for standard neutrino detectors. The
measurement of CEvNS has now become feasible, thanks to the development of
ultra-sensitive technology for rare decay and weakly-interacting massive
particle (dark matter) searches. The CEvNS cross section is cleanly predicted
in the standard model; hence its measurement provides a standard model test. It
is relevant for supernova physics and supernova-neutrino detection, and enables
validation of dark-matter detector background and detector-response models. In
the long term, precision measurement of CEvNS will address questions of nuclear
structure. COHERENT will deploy multiple detector technologies in a phased
approach: a 14-kg CsI[Na] scintillating crystal, 15 kg of p-type point-contact
germanium detectors, and 100 kg of liquid xenon in a two-phase time projection
chamber. Following an extensive background measurement campaign, a location in
the SNS basement has proven to be neutron-quiet and suitable for deployment of
the COHERENT detector suite. The simultaneous deployment of the three COHERENT
detector subsystems will test the $N^2$ dependence of the cross section and
ensure an unambiguous discovery of CEvNS. This document describes concisely the
COHERENT physics motivations, sensitivity and plans for measurements at the SNS
to be accomplished on a four-year timescale.
[Show abstract][Hide abstract] ABSTRACT: Antineutrino monitoring of nuclear reactors has been demonstrated many times (Klimov et al., 1994 ; Bowden et al., 2009 ; Oguri et al., 2014 ), 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)  and .
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2015; 769. DOI:10.1016/j.nima.2014.09.073 · 1.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 11/2014; 771. DOI:10.1016/j.nima.2014.10.022 · 1.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory,
Tennessee, provides an intense flux of neutrinos in the few tens-of-MeV range,
with a sharply-pulsed timing structure that is beneficial for background
rejection. In this white paper, we describe how the SNS source can be used for
a measurement of coherent elastic neutrino-nucleus scattering (CENNS), and the
physics reach of different phases of such an experimental program (CSI:
Coherent Scattering Investigations at the SNS).
[Show abstract][Hide abstract] ABSTRACT: Detecting antineutrinos emitted from nuclear reactors has been
previously demonstrated as a monitor of fuel content and usage. The
continuous fuel cycle of a CANDU on-load reactor presents a unique
challenge for monitoring. We present the calibration and
characterization of a detector designed for this task. The detector will
be deployed Fall 2012 at Point Lepreau Generating Station.
[Show abstract][Hide abstract] ABSTRACT: Nuclear reactors have served as the neutrino source for many fundamental physics experiments. The techniques developed by these experiments make it possible to use these very weakly interacting particles for a practical purpose. The large flux of antineutrinos that leaves a reactor carries information about two quantities of interest for safeguards: the reactor power and fissile inventory. Our SNL/LLNL collaboration has demonstrated that such antineutrino based monitoring is feasible using a relatively small cubic meter scale liquid scintillator detector at tens of meters standoff from a commercial Pressurized Water Reactor (PWR). With little or no burden on the plant operator we have been able to remotely and automatically monitor the reactor operational status (on/off), power level, and fuel burnup. The initial detector was deployed in an underground gallery that lies directly under the containment dome of an operating PWR. The gallery is 25 meters from the reactor core center, is rarely accessed by plant personnel, and provides a muon-screening effect of some 20–30 meters of water equivalent earth and concrete overburden. Unfortunately, many reactor facilities do not contain an equivalent underground location. We have therefore attempted to construct a complete detector system which would be capable of operating in an aboveground location and could be transported to a reactor facility with relative ease. A standard 6-meter shipping container was used as our transportable laboratory — containing active and passive shielding components, the antineutrino detector and all electronics, as well as climate control systems. This aboveground system was deployed and tested at the San Onofre Nuclear Generating Station (SONGS) in southern California in 2010 and early 2011. We will first present an overview of the initial demonstrations of our belowground detector. Then we will describe the aboveground system and the technological developments of the two antineutrino detectors that were deployed. Finally, some preliminary results of our aboveground test will be shown.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: The large flux of neutrinos that leaves a nuclear reactor carries information about two quantities of interest for safeguards: the reactor power and fissile inventory. Our SNL/LLNL collaboration has demonstrated that antineutrino-based nuclear reactor monitoring is feasible using a relatively small cubic scale detector made of Gadolinium loaded liquid scintillator at tens of meters standoff from a commercial Pressurized Water Reactor, deployed in an underground gallery that lies directly under the containment. Recently we have investigated several technologies paths that could allow such devices to be more readily deployed in the field - of particular concern to reactor operators and safeguards practitioners is the flammability of the Gd doped liquid scintillator. In addition, many PWR facilities do not have an available underground gallery to provide the screening of muon induced backgrounds. As a result, we have developed and fielded three new detectors: a low cost, non-flammable water based design; a robust solid-state design based upon plastic scintillator; and a smaller cryogenic detector based on ultra-high purity Germanium. All three of these technologies have been deployed at our below-ground facility at the San Onofre Nuclear Generating Station in southern California. We first present an overview of the use of antineutrinos in reactor monitoring. We then explain the detection mechanism based on inverse beta decay and the dominant sources of above-ground background that would contaminate this signal. Next, we discuss conceptual ideas under consideration for a future aboveground detector. Separate sections are devoted to describe the design, construction and deployment of each of our three new technologies that have already been deployment. We discuss the various levels of sensitivity to the reactor antineutrino signature that each of these detectors was able to demonstrate and the tradeoffs that accompany them.
[Show abstract][Hide abstract] ABSTRACT: Fission reactors emit large numbers of antineutrinos and this flux may be useful for the measurement of two quantities of interest for reactor safeguards: the reactor's power and plutonium inventory throughout its cycle. The high antineutrino flux and relatively low background rates means that simple cubic meter scale detectors at tens of meters standoff can record hundreds or thousands of antineutrino events per day. Such antineutrino detectors would add online, quasi-real-time bulk material accountancy to the set of reactor monitoring tools available to the IAEA and other safeguards agencies with minimal impact on reactor operations. Between 2003 and 2008, our LLNL/SNL collaboration successfully deployed several prototype safeguards detectors at a commercial reactor in order to test both the method and the practicality of its implementation in the field. Partially on the strength of the results obtained from these deployments, an Experts Meeting was convened by the IAEA Novel Technologies Group in 2008 to assess current antineutrino detection technology and examine how it might be incorporated into the safeguards regime. Here we present a summary of our previous deployments and discuss current work that seeks to provide expanded capabilities suggested by the Experts Panel, in particular aboveground detector operation.