224 research outputs found
Improved TPB-coated Light Guides for Liquid Argon TPC Light Detection Systems
Scintillation light produced in liquid argon (LAr) must be shifted from 128
nm to visible wavelengths in light detection systems used for liquid argon
time-projection chambers (LArTPCs). To date, LArTPC light collection systems
have employed tetraphenyl butadiene (TPB) coatings on photomultiplier tubes
(PMTs) or plates placed in front of the PMTs. Recently, a new approach using
TPB-coated light guides was proposed. In this paper, we report on light guides
with improved attenuation lengths above 100 cm when measured in air. This is an
important step in the development of meter-scale light guides for future
LArTPCs. Improvements come from using a new acrylic-based coating,
diamond-polished cast UV transmitting acrylic bars, and a hand-dipping
technique to coat the bars. We discuss a model for connecting bar response in
air to response in liquid argon and compare this to data taken in liquid argon.
The good agreement between the prediction of the model and the measured
response in liquid argon demonstrates that characterization in air is
sufficient for quality control of bar production. This model can be used in
simulations of light guides for future experiments.Comment: 25 pages, 20 figure
Demonstration of a Lightguide Detector for Liquid Argon TPCs
We report demonstration of light detection in liquid argon using an acrylic
lightguide detector system. This opens the opportunity for development of an
inexpensive, large-area light collection system for large liquid argon time
projection chambers. The guides are constructed of acrylic, with TPB embedded
in a surface coating with a matching index of refraction. We study the response
to early scintillation light produced by a 5.3 MeV alpha. We measure coating
responses from 7 to 8 PE on average, compared to an ideal expectation of 10 PE
on average. We estimate the attenuation length of light along the lightguide
bar to be greater than 0.5 m. The coating response and the attenuation length
can be improved; we show, however, that these results are already sufficient
for triggering in a large detector
Benchmarking TPB-coated Light Guides for Liquid Argon TPC Light Detection Systems
Scintillation light from liquid argon is produced at 128 nm and thus must be shifted to visible wavelengths in light detection systems used for Liquid Argon Time Projection Chambers (LArTPCs). To date, designs have employed tetraphenyl butadiene (TPB) coatings on photomultiplier tubes (PMTs) or plates placed in front of the PMTs. Recently, a new approach using TPB-coated light guides was proposed. In this paper, we show that the response of lightguides coated with TPB in a UV Transmitting (UVT) acrylic matrix is very similar to that of a coating using a polystyrene (PS) matrix. We obtain a factor of three higher light yield than has been previously reported from lightguides. This paper provides information on the response of the lightguides so that these can be modeled in simulations for future LArTPCs. This paper also identifies areas of R&D for potential improvements in the lightguide respons
On two weak CC Delta production models
We perform a detail analysis of two models of neutrino CC Delta production on
free nucleons. First model is a standard one based on nucleon-Delta transition
current with several form-factors. Second model is a starting point for a
construction of Marteau model with sophisticated analytical computations of
nuclear effects. We conclude that both models lead to similar results.Comment: 9 pages, includes 9 figures, accepted for publication in J. Phys.
Environmental Effects on TPB Wavelength-Shifting Coatings
The scintillation detection systems of liquid argon time projection chambers
(LArTPCs) require wavelength shifters to detect the 128 nm scintillation light
produced in liquid argon. Tetraphenyl butadiene (TPB) is a fluorescent material
that can shift this light to a wavelength of 425 nm, lending itself well to use
in these detectors. We can coat the glass of photomultiplier tubes (PMTs) with
TPB or place TPB-coated plates in front of the PMTs.
In this paper, we investigate the degradation of a chemical TPB coating in a
laboratory or factory environment to assess the viability of long-term TPB film
storage prior to its initial installation in an LArTPC. We present evidence for
severe degradation due to common fluorescent lights and ambient sunlight in
laboratories, with potential losses at the 40% level in the first day and
eventual losses at the 80% level after a month of exposure. We determine the
degradation is due to wavelengths in the UV spectrum, and we demonstrate
mitigating methods for retrofitting lab and factory environments
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