193 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
Weighted MCRDR: Deriving Information about Relationships between Classifications in MCRDR.
Multiple Classification Ripple Down Rules (MCRDR) is a
knowledge acquisition technique that produces representations, or knowledge maps, of a human expert's knowledge of a particular domain. However, work on gaining an understanding of the knowledge acquired at a deeper meta-level or using the knowledge to derive new information is still in its infancy. This paper will introduce a technique called Weighted MCRDR (WM), which looks at deriving and learning information about the relationships between multiple classifications within MCRDR by calculating a meaningful rating for the task at hand. This is not intended to reduce the knowledge acquisition effort for the expert. Rather, it is attempting to use the knowledge received in the MCRDR knowledge map to derive additional information that can allow improvements in functionality of MCRDR in many problem domains. Preliminary testing shows that there exists a strong potential for WM to quickly and effectively learn meaningful weightings
An Augmentation Hybrid System for Document Classification and Rating.
This paper introduces an augmentation hybrid system, referred to as Rated MCRDR. It uses Multiple Classification Ripple Down Rules (MCRDR), a simple and effective knowledge acquisition technique, combined with a neural network
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,
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