1,203 research outputs found
Optical Properties of Quantum-Dot-Doped Liquid Scintillators
Semiconductor nanoparticles (quantum dots) were studied in the context of
liquid scintillator development for upcoming neutrino experiments. The unique
optical and chemical properties of quantum dots are particularly promising for
the use in neutrinoless double beta decay experiments. Liquid scintillators for
large scale neutrino detectors have to meet specific requirements which are
reviewed, highlighting the peculiarities of quantum-dot-doping. In this paper,
we report results on laboratory-scale measurements of the attenuation length
and the fluorescence properties of three commercial quantum dot samples. The
results include absorbance and emission stability measurements, improvement in
transparency due to filtering of the quantum dot samples, precipitation tests
to isolate the quantum dots from solution and energy transfer studies with
quantum dots and the fluorophore PPO.Comment: version 2, minor text update
Transit Time and Charge Correlations of Single Photoelectron Events in R7081 PMTs
During the calibration phase of the photomultiplier tubes (PMT) for the
Double Chooz experiment the PMT response to light with single photoelectron
(SPE) intensity was analysed. With our setup we were able to measure the
combined transit time and charge response of the PMT and therefore we could
deconstruct and analyse all physical effects having an influence on the PMT
signal. Based on this analysis charge and time correlated probability density
functions were developed to include the PMT response in a Monte Carlo
simulation.Comment: minor changes by referee reques
Large scale Gd-beta-diketonate based organic liquid scintillator production for antineutrino detection
Over the course of several decades, organic liquid scintillators have formed
the basis for successful neutrino detectors. Gadolinium-loaded liquid
scintillators provide efficient background suppression for electron
antineutrino detection at nuclear reactor plants. In the Double Chooz reactor
antineutrino experiment, a newly developed beta-diketonate gadolinium-loaded
scintillator is utilized for the first time. Its large scale production and
characterization are described. A new, light yield matched metal-free companion
scintillator is presented. Both organic liquids comprise the target and "Gamma
Catcher" of the Double Chooz detectors.Comment: 16 pages, 4 figures, 5 table
Large scale Gd-beta-diketonate based organic liquid scintillator production for antineutrino detection
Over the course of several decades, organic liquid scintillators have formed
the basis for successful neutrino detectors. Gadolinium-loaded liquid
scintillators provide efficient background suppression for electron
antineutrino detection at nuclear reactor plants. In the Double Chooz reactor
antineutrino experiment, a newly developed beta-diketonate gadolinium-loaded
scintillator is utilized for the first time. Its large scale production and
characterization are described. A new, light yield matched metal-free companion
scintillator is presented. Both organic liquids comprise the target and "Gamma
Catcher" of the Double Chooz detectors.Comment: 16 pages, 4 figures, 5 table
Large scale Gd-beta-diketonate based organic liquid scintillator production for antineutrino detection
Over the course of several decades, organic liquid scintillators have formed
the basis for successful neutrino detectors. Gadolinium-loaded liquid
scintillators provide efficient background suppression for electron
antineutrino detection at nuclear reactor plants. In the Double Chooz reactor
antineutrino experiment, a newly developed beta-diketonate gadolinium-loaded
scintillator is utilized for the first time. Its large scale production and
characterization are described. A new, light yield matched metal-free companion
scintillator is presented. Both organic liquids comprise the target and "Gamma
Catcher" of the Double Chooz detectors.Comment: 16 pages, 4 figures, 5 table
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No. 6: Navaho and Ute Peyotism: A Chronological and Distributional Study
Spectral fingerprinting for specific algal groups on sediments in situ: a new sensor
Currently it is still extremely difficult to adequately sample populations of microalgae on sediments for large-scale biomass determination. We have now devised a prototype of a new benthic sensor (BenthoFluor) for the quantitative and qualitative assessment of microphytobenthos populations in situ. This sensor enables a high spatial and temporal resolution and a rapid evaluation of the community structure and distribution. These determinations are based on the concept that five spectral excitation ranges can be used to differentiate groups of microalgae, in situ, within a few seconds. In addition, because sediments contain a lot of yellow substances, which can affect the fluorescence and optical differentiation of the algae, the device was equipped with a UV-LED for yellow substances correction. The device was calibrated against HPLC with cultures and tested in the field. Our real-time approach can be used to monitor algal assemblage composition on sediments and is an ideal tool for investigations on the large-scale spatial and temporal variation of algal populations in sediments. Apart from the differentiation of algal populations, the BenthoFluor allows instantaneous monitoring of the chlorophyll concentrations and determination of which algae are responsible for this on the uppermost surface of sediments in the field and in experimental set-ups
A new method for imaging nuclear threats using cosmic ray muons
Muon tomography is a technique that uses cosmic ray muons to generate three
dimensional images of volumes using information contained in the Coulomb
scattering of the muons. Advantages of this technique are the ability of cosmic
rays to penetrate significant overburden and the absence of any additional dose
delivered to subjects under study above the natural cosmic ray flux.
Disadvantages include the relatively long exposure times and poor position
resolution and complex algorithms needed for reconstruction. Here we
demonstrate a new method for obtaining improved position resolution and
statistical precision for objects with spherical symmetry
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