[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: The design and performance of the LUX-ZEPLIN (LZ) detector is described as of
March 2015 in this Conceptual Design Report. LZ is a second-generation
dark-matter detector with the potential for unprecedented sensitivity to weakly
interacting massive particles (WIMPs) of masses from a few GeV/c2 to hundreds
of TeV/c2. With total liquid xenon mass of about 10 tonnes, LZ will be the most
sensitive experiment for WIMPs in this mass region by the end of the decade.
This report describes in detail the design of the LZ technical systems.
Expected backgrounds are quantified and the performance of the experiment is
presented. The LZ detector will be located at the Sanford Underground Research
Facility in South Dakota. The organization of the LZ Project and a summary of
the expected cost and current schedule are given.
[Show abstract][Hide abstract] ABSTRACT: The RED-100 two-phase liquid xenon emission detector is developed today for the experiment aimed at searching for elastic coherent neutrino scattering off atomic nuclei. The main elements of the photodetector system of the RED-100 detector are Hamamatsu R11410-20 photomultiplier tubes (PMTs) dedicated for low-background experiments and liquid xenon environment. The basic characteristics of the PMTs are investigated, in particular, noise pulses and afterpulses, which may cause difficulties in searching for rare events. Amplitude distributions of the noise pulses and time distributions of the afterpulses, as well as the dependences of the noise pulse rate on the PMT bias voltage and the temperature are presented.
[Show abstract][Hide abstract] ABSTRACT: We have shown that high voltage biased Hamamatsu R11410-20 photomultipliers
with a dark count rate above 10 kHz emit single photons. The effect has been
observed in a few units at room temperature and temperatures reduced down to
-60 degrees Celsius. The effect should be taken into account in experiments
aimed on search for rare events with small energy depositions in massive liquid
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 04/2015; 794. DOI:10.1016/j.nima.2015.04.066 · 1.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A two-phase emission detector containing 5 kg of liquid Xe is installed at the horizontal experimental channel of the research nuclear reactor IRT MEPhI to measure the liquid Xe response to nuclei recoils with kinetic energies below 1 keV. Preliminary tests have demonstrated that ≥ 15 μs electron lifetime in liquid Xe and ~ 10 photoelectrons single ionization electron signal are achieved. These parameters are sufficient to detect and identify events at the single electron level.
[Show abstract][Hide abstract] ABSTRACT: A control circuit for the operation of Hamamatsu R11410-20 photomultiplier tubes (PMTs), which is intended for use in the RED 100 liquid-xenon emission detector, was developed. To prevent the photocathode degradation due to intense flashes that are associated with signals from high-energy cosmic-ray muons, the circuit forms a voltage pulse that is fed to the PMT photocathode and “blocks” the interelectrode gap between the photocathode and the first dynode. Thus, electron current through this gap is stopped for some time, which suffices for the complete collection of ionization electrons in the RED 100 detector after a cosmic muon passes its sensitive volume. The parameters of the circuit are selected such that the PMT relaxation time after the termination of a blocking pulse, which is determined by the transient processes in the divider, is ∼200 μs for a divider with a total resistance of 20 MΩ. This is acceptable for the intended application of the RED 100 detector in an experiment on the search for coherent neutrino scattering off xenon nuclei.
[Show abstract][Hide abstract] ABSTRACT: We present the results of the first experimental study of ionization yield of
electron recoils with energies below 100 keV produced in liquid xenon by the
isotopes: 37Ar, 83mKr, 241Am, 129Xe, 131Xe. It is confirmed by a direct
measurement with 37Ar isotope (2.82 keV) that the ionization yield is growing
up with the energy decrease in the energy range below ~ 10 keV accordingly to
the NEST predictions. Decay time of scintillation at 2.82 keV is measured to be
25 +/- 3 ns at the electric field of 3.75 kV/cm.
Journal of Instrumentation 08/2014; 9(11). DOI:10.1088/1748-0221/9/11/P11014 · 1.40 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: We present results from the measurement of the neutron production rate in lead by high energy cosmic-ray muons at a depth of 2850 m water equivalent (mean muon energy of 260 GeV). A tonne-scale highly segmented plastic scintillator detector was utilised to detect both the energy depositions from the traversing muons as well as the delayed radiative capture signals of the induced neutrons. Complementary Monte Carlo simulations reproduce well the distributions of muons and detected muon-induced neutrons. Absolute agreement between simulation and data is of the order of 25%. By comparing the measured and simulated neutron capture rates a neutron yield in pure lead of
neutrons/muon/(g/cm2) has been obtained.
LOW RADIOACTIVITY TECHNIQUES 2013 (LRT 2013): Proceedings of the IV International Workshop in Low Radioactivity Techniques; 08/2013
[Show abstract][Hide abstract] ABSTRACT: A successful operation of a new optical readout system (THGEM + WLS + MGPDs
(multichannel array of multipixel avalanche Geiger photodiodes) in a two-phase
liquid xenon detector was demonstrated.
Journal of Instrumentation 03/2013; 8(05). DOI:10.1088/1748-0221/8/05/P05017 · 1.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A measurement is presented of the neutron production rate in lead by high
energy cosmic-ray muons at a depth of 2850 m water equivalent (w.e.) and a mean
muon energy of 260 GeV. The measurement exploits the delayed coincidences
between muons and the radiative capture of induced neutrons in a highly
segmented tonne scale plastic scintillator detector. Detailed Monte Carlo
simulations reproduce well the measured capture times and multiplicities and,
within the dynamic range of the instrumentation, the spectrum of energy
deposits. By comparing measurements with simulations of neutron capture rates a
neutron yield in lead of (5.8 +/- 0.2) x 10^-3 neutrons/muon/(g/cm^2) has been
obtained. Absolute agreement between simulation and data is of order 25%.
Consequences for deep underground rare event searches are discussed.
[Show abstract][Hide abstract] ABSTRACT: Development study of a wavelength shifter (WLS) to convert a noble gas emission light from the VUV region to the visible range is presented. The shifter is developed for the use with an array of blue-sensitive multipixel avalanche Geiger photodiodes (MRS APD) to detect Xe 175 nm emission. It was found that a polycrystalline p-terphenyl having an absorption peak at 180 nm with a molar extinction coefficient ε of 37500±5000 mol−1·l cm−1 is well suited for this. To satisfy a requirement of compatibility with an extra pure noble gas detection medium the p-terphenyl layer was coated with an ∼1 μm thick poly-para-xylylene protection film.
Keywords: VUV detection; Wavelength shifter; Noble gas emission
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 12/2012; 695:403-406. DOI:10.1016/j.nima.2011.12.036 · 1.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We propose to detect and to study neutrino neutral current coherent
scattering off atomic nuclei with a two-phase emission detector using liquid
xenon as a working medium. Expected signals and backgrounds are calculated for
two possible experimental sites: Kalinin Nuclear Power Plant in the Russian
Federation and Spallation Neutron Source at the Oak Ridge National Laboratory
in the USA. Both sites have advantages as well as limitations. However the
experiment looks feasible at either location. Preliminary design of the
detector and supporting R&D program are discussed.
Journal of Instrumentation 12/2012; 8(10). DOI:10.1088/1748-0221/8/10/P10023 · 1.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Two-phase Cryogenic Avalanche Detectors (CRADs) with GEM and THGEM
multipliers have become an emerging potential technique for charge recording in
rare-event experiments. In this work we present the performance of two-phase
CRADs operated in Ar and Ar+N2. Detectors with sensitive area of 10x10 cm2,
reaching a litre-scale active volume, yielded gains of the order of 1000 with a
double-THGEM multiplier. Higher gains, of about 5000, have been attained in
two-phase Ar CRADs with a hybrid triple-stage multiplier, comprising of a
double-THGEM followed by a GEM. The performance of two-phase CRADs in Ar doped
with N2 (0.1-0.6%) yielded faster signals and similar gains compared to the
operation in two-phase Ar. The applicability to rare-event experiments is
Journal of Instrumentation 10/2012; 8(02). DOI:10.1088/1748-0221/8/02/P02008 · 1.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A technique for studying single-electron noise in emission detectors that are intended for detection of rare processes with small energy releases is developed. Examples of possible applications are experiments for search of dark matter in the Universe and detection of reactor antineutrinos via coherent neutrino scattering at heavy xenon nuclei. We present the first results of studying the nature of single-electron noise in a liquid-xenon emission detector and consider possible ways to suppress it.
[Show abstract][Hide abstract] ABSTRACT: We studied the application of statistical reconstruction algorithms, namely
maximum likelihood and least squares methods, to the problem of event
reconstruction in a dual phase liquid xenon detector. An iterative method was
developed for in-situ reconstruction of the PMT light response functions from
calibration data taken with an uncollimated gamma-ray source. Using the
techniques described, the performance of the ZEPLIN-III dark matter detector
was studied for 122 keV gamma-rays. For the inner part of the detector (R<100
mm), spatial resolutions of 13 mm and 1.6 mm FWHM were measured in the
horizontal plane for primary and secondary scintillation, respectively. An
energy resolution of 8.1% FWHM was achieved at that energy. The possibility of
using this technique for improving performance and reducing cost of
scintillation cameras for medical applications is currently under study.
[Show abstract][Hide abstract] ABSTRACT: ZEPLIN-III is a two-phase xenon direct dark matter experiment located at the
Boulby Mine (UK). After its first science run in 2008 it was upgraded with: an
array of low background photomultipliers, a new anti-coincidence detector
system with plastic scintillator and an improved calibration system. After 319
days of data taking the second science run ended in May 2011. In this paper we
describe the instrument performance with emphasis on the position and energy
reconstruction algorithm and summarise the final science results.
Journal of Instrumentation 11/2011; 7(03). DOI:10.1088/1748-0221/7/03/C03044 · 1.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Plastic scintillators are widely used in industry, medicine and scientific
research, including nuclear and particle physics. Although one of their most
common applications is in neutron detection, experimental data on their
response to low-energy nuclear recoils are scarce. Here, the relative
scintillation efficiency for neutron-induced nuclear recoils in a
polystyrene-based plastic scintillator (UPS-923A) is presented, exploring
recoil energies between 125 keV and 850 keV. Monte Carlo simulations,
incorporating light collection efficiency and energy resolution effects, are
used to generate neutron scattering spectra which are matched to observed
distributions of scintillation signals to parameterise the energy-dependent
quenching factor. At energies above 300 keV the dependence is reasonably
described using the semi-empirical formulation of Birks and a kB factor of
(0.014+/-0.002) g/MeVcm^2 has been determined. Below that energy the measured
quenching factor falls more steeply than predicted by the Birks formalism.
Physical Review C 11/2011; 85(6). DOI:10.1103/PhysRevC.85.065801 · 3.73 Impact Factor