135 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
A comparison of the neutron detection efficiency and response characteristics of two pixelated PSD-capable organic scintillator detectors with different photo-detection readout methods
We characterize the performance of two pixelated neutron detectors: a
PMT-based array that utilizes Anger logic for pixel identification and a
SiPM-based array that employs individual pixel readout. The SiPM-based array
offers improved performance over the previously developed PMT-based detector
both in terms of uniformity and neutron detection efficiency. Each detector
array uses PSD-capable plastic scintillator as a detection medium. We describe
the calibration and neutron efficiency measurement of both detectors using a
Cs source for energy calibration and a Cf source for
calibration of the neutron response. We find that the intrinsic neutron
detection efficiency of the SiPM-based array is ()\%, which
is almost twice that of the PMT-based array, which we measure to be ()\%
A Note on Neutron Capture Correlation Signals, Backgrounds, and Efficiencies
A wide variety of detection applications exploit the timing correlations that
result from the slowing and eventual capture of neutrons. These include
capture-gated neutron spectrometry, multiple neutron counting for fissile
material detection and identification, and antineutrino detection. There are
several distinct processes that result in correlated signals in these
applications. Depending on the application, one class of correlated events can
be a background that is difficult to distinguish from the class that is of
interest. Furthermore, the correlation timing distribution depends on the
neutron capture agent and detector geometry. Here, we explain the important
characteristics of the neutron capture timing distribution, making reference to
simulations and data from a number of detectors currently in use or under
development. We point out several features that may assist in background
discrimination, and that must be carefully accounted for if accurate detection
efficiencies are to be quoted.Comment: 7 pages, 7 figures; Submitted to Nuclear Instrument and Methods
Status of the LUX Dark Matter Search
The Large Underground Xenon (LUX) dark matter search experiment is currently
being deployed at the Homestake Laboratory in South Dakota. We will highlight
the main elements of design which make the experiment a very strong competitor
in the field of direct detection, as well as an easily scalable concept. We
will also present its potential reach for supersymmetric dark matter detection,
within various timeframes ranging from 1 year to 5 years or more.Comment: 4 pages, in proceedings of the SUSY09 conferenc
After LUX: The LZ Program
The LZ program consists of two stages of direct dark matter searches using
liquid Xe detectors. The first stage will be a 1.5-3 tonne detector, while the
last stage will be a 20 tonne detector. Both devices will benefit tremendously
from research and development performed for the LUX experiment, a 350 kg liquid
Xe dark matter detector currently operating at the Sanford Underground
Laboratory. In particular, the technology used for cryogenics and electrical
feedthroughs, circulation and purification, low-background materials and
shielding techniques, electronics, calibrations, and automated control and
recovery systems are all directly scalable from LUX to the LZ detectors.
Extensive searches for potential background sources have been performed, with
an emphasis on previously undiscovered background sources that may have a
significant impact on tonne-scale detectors. The LZ detectors will probe
spin-independent interaction cross sections as low as 5E-49 cm2 for 100 GeV
WIMPs, which represents the ultimate limit for dark matter detection with
liquid xenon technology.Comment: Conference proceedings from APS DPF 2011. 9 pages, 6 figure
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