207 research outputs found
Study of wavelength-shifting chemicals for use in large-scale water Cherenkov detectors
Cherenkov detectors employ various methods to maximize light collection at
the photomultiplier tubes (PMTs). These generally involve the use of highly
reflective materials lining the interior of the detector, reflective materials
around the PMTs, or wavelength-shifting sheets around the PMTs. Recently, the
use of water-soluble wavelength-shifters has been explored to increase the
measurable light yield of Cherenkov radiation in water. These wave-shifting
chemicals are capable of absorbing light in the ultravoilet and re-emitting the
light in a range detectable by PMTs. Using a 250 L water Cherenkov detector, we
have characterized the increase in light yield from three compounds in water:
4-Methylumbelliferone, Carbostyril-124, and Amino-G Salt. We report the gain in
PMT response at a concentration of 1 ppm as: 1.88 0.02 for
4-Methylumbelliferone, stable to within 0.5% over 50 days, 1.37 0.03 for
Carbostyril-124, and 1.20 0.02 for Amino-G Salt. The response of
4-Methylumbelliferone was modeled, resulting in a simulated gain within 9% of
the experimental gain at 1 ppm concentration. Finally, we report an increase in
neutron detection performance of a large-scale (3.5 kL) gadolinium-doped water
Cherenkov detector at a 4-Methylumbelliferone concentration of 1 ppm.Comment: 7 pages, 9 figures, Submitted to Nuclear Instruments and Methods
Transparency of 0.2% GdCl3 Doped Water in a Stainless Steel Test Environment
The possibility of neutron and neutrino detection using water Cerenkov
detectors doped with gadolinium holds the promise of constructing very large
high-efficiency detectors with wide-ranging application in basic science and
national security. This study addressed a major concern regarding the
feasibility of such detectors: the transparency of the doped water to the
ultraviolet Cerenkov light. We report on experiments conducted using a 19-meter
water transparency measuring instrument and associated materials test tank.
Sensitive measurements of the transparency of water doped with 0.2% GdCl3 at
337nm, 400nm and 420nm were made using this instrument. These measurements
indicate that GdCl3 is not an appropriate dopant in stainless steel constructed
water Cerenkov detectors.Comment: 17 pages, 11 figures, corrects typos, changes formatting, adds error
bars to figure
Observation of Neutrons with a Gadolinium Doped Water Cerenkov Detector
Spontaneous and induced fission in Special Nuclear Material (SNM) such as
235U and 239Pu results in the emission of neutrons and high energy gamma-rays.
The multiplicities of and time correlations between these particles are both
powerful indicators of the presence of fissile material. Detectors sensitive to
these signatures are consequently useful for nuclear material monitoring,
search, and characterization. In this article, we demonstrate sensitivity to
both high energy gamma-rays and neutrons with a water Cerenkov based detector.
Electrons in the detector medium, scattered by gamma-ray interactions, are
detected by their Cerenkov light emission. Sensitivity to neutrons is enhanced
by the addition of a gadolinium compound to the water in low concentrations.
Cerenkov light is similarly produced by an 8 MeV gamma-ray cascade following
neutron capture on the gadolinium. The large solid angle coverage and high
intrinsic efficiency of this detection approach can provide robust and low cost
neutron and gamma-ray detection with a single device.Comment: 7 pages, 4 figures. Submitted to Nuclear Instruments and Methods,
Reconstructing the direction of reactor antineutrinos via electron scattering in Gd-doped water Cherenkov detectors
The potential of elastic antineutrino-electron scattering in a Gd-doped water
Cherenkov detector to determine the direction of a nuclear reactor antineutrino
flux was investigated using the recently proposed WATCHMAN antineutrino
experiment as a baseline model. The expected scattering rate was determined
assuming a 13-km standoff from a 3.758-GWt light water nuclear reactor and the
detector response was modeled using a Geant4-based simulation package.
Background was estimated via independent simulations and by scaling published
measurements from similar detectors. Background contributions were estimated
for solar neutrinos, misidentified reactor-based inverse beta decay
interactions, cosmogenic radionuclides, water-borne radon, and gamma rays from
the photomultiplier tubes (PMTs), detector walls, and surrounding rock. We show
that with the use of low background PMTs and sufficient fiducialization,
water-borne radon and cosmogenic radionuclides pose the largest threats to
sensitivity. Directional sensitivity was then analyzed as a function of radon
contamination, detector depth, and detector size. The results provide a list of
experimental conditions that, if satisfied in practice, would enable
antineutrino directional reconstruction at 3 significance in large
Gd-doped water Cherenkov detectors with greater than 10-km standoff from a
nuclear reactor.Comment: 11 pages, 9 figure
Reactor monitoring and safeguards using antineutrino detectors
Nuclear reactors have served as the antineutrino 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. Measurements made with antineutrino detectors could
therefore offer an alternative means for verifying the power history and
fissile inventory of a reactors, as part of International Atomic Energy Agency
(IAEA) and other reactor safeguards regimes. Several efforts to develop this
monitoring technique are underway across the globe.Comment: 6 pages, 4 figures, Proceedings of XXIII International Conference on
Neutrino Physics and Astrophysics (Neutrino 2008); v2: minor additions to
reference
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