223 research outputs found
ArCLight - a Compact Dielectric Large-Area Photon Detector
ArCLight is a novel device for detecting scintillation light over large areas
with Photon Detection Efficiency (PDE) of the order of a few percent. Its
robust technological design allows for efficient use in large-volume particle
detectors, such as Liquid Argon Time Projection Chambers (LArTPCs) or liquid
scintillator detectors. Due to its dielectric structure it can be placed inside
volumes with high electric field. It could potentially replace vacuum
PhotoMultiplier Tubes (PMTs) in applications where high PDE is not required.
The photon detection efficiency for a 10x10cm2 detector prototype was measured
to be in the range of 0.8% to 2.2% across the active area
A method to suppress dielectric breakdowns in liquid argon ionization detectors for cathode to ground distances of several millimeters
We present a method to reach electric field intensity as high as 400 kV/cm in
liquid argon for cathode-ground distances of several millimeters. This can be
achieved by suppressing field emission from the cathode, overcoming limitations
that we reported earlier
Measurement of the drift field in the ARGONTUBE LAr TPC with 266~nm pulsed laser beams
ARGONTUBE is a liquid argon time projection chamber (LAr TPC) with a drift
field generated in-situ by a Greinacher voltage multiplier circuit. We present
results on the measurement of the drift-field distribution inside ARGONTUBE
using straight ionization tracks generated by an intense UV laser beam. Our
analysis is based on a simplified model of the charging of a multi-stage
Greinacher circuit to describe the voltages on the field cage rings
On the Electric Breakdown in Liquid Argon at Centimeter Scale
We present a study on the dependence of electric breakdown discharge
properties on electrode geometry and the breakdown field in liquid argon near
its boiling point. The measurements were performed with a spherical cathode and
a planar anode at distances ranging from 0.1 mm to 10.0 mm. A detailed study of
the time evolution of the breakdown volt-ampere characteristics was performed
for the first time. It revealed a slow streamer development phase in the
discharge. The results of a spectroscopic study of the visible light emission
of the breakdowns complement the measurements. The light emission from the
initial phase of the discharge is attributed to electro-luminescence of liquid
argon following a current of drifting electrons. These results contribute to
set benchmarks for breakdown-safe design of ionization detectors, such as
Liquid Argon Time Projection Chambers (LAr TPC).Comment: Minor revision according to editor report. 17 pages, 15 figures, 2
tables. Turboencabulato
First Demonstration of a Pixelated Charge Readout for Single-Phase Liquid Argon Time Projection Chambers
Liquid Argon Time Projection Chambers (LArTPCs) have been selected for the
future long-baseline Deep Underground Neutrino Experiment (DUNE). To allow
LArTPCs to operate in the high-multiplicity near detector environment of DUNE,
a new charge readout technology is required. Traditional charge readout
technologies introduce intrinsic ambiguities, combined with a slow detector
response, these ambiguities have limited the performance of LArTPCs, until now.
Here, we present a novel pixelated charge readout that enables the full 3D
tracking capabilities of LArTPCs. We characterise the signal to noise ratio of
charge readout chain, to be about 14, and demonstrate track reconstruction on
3D space points produced by the pixel readout. This pixelated charge readout
makes LArTPCs a viable option for the DUNE near detector complex.Comment: 13 pages, 9 figure
Pharmacological profile of methylphenidate-based designer drugs
Methylphenidate-based designer drugs are new psychoactive substances (NPS) that are used outside medical settings and their pharmacology is largely unexplored. The aim of the present study was to characterize the pharmacology of methylphenidate-based substances in vitro.; We determined the potencies of the methylphenidate-based NPS N-benzylethylphenidate, 3,4-dichloroethylphenidate, 3,4-dichloromethylphenidate, ethylnaphthidate, ethylphenidate, 4-fluoromethylphenidate, isopropylphenidate, 4-methylmethylphenidate, methylmorphenate, and propylphenidate and the potencies of the related compounds cocaine and modafinil with respect to norepinephrine, dopamine, and serotonin transporter inhibition in transporter-transfected human embryonic kidney 293 cells. We also investigated monoamine efflux and monoamine receptor and transporter binding affinities. Furthermore, we assessed the cell integrity under assay conditions.; All methylphenidate-based substances inhibited the norepinephrine and dopamine transporters 4 to >1000-fold more potently than the serotonin transporter. Similar to methylphenidate and cocaine, methylphenidate-based NPS did not elicit transporter-mediated efflux of monoamines. Besides binding to monoamine transporters, several test drugs had affinity for adrenergic, serotonergic, and rat trace amine-associated receptors but not for dopaminergic or mouse trace amine-associated receptors. No cytotoxicity was observed after drug treatment at assay concentrations.; Methylphenidate-based substances had pharmacological profiles similar to methylphenidate and cocaine. The predominant actions on dopamine transporters vs. serotonin transporters may be relevant when considering abuse liability
Stereochemistry of phase-1 metabolites of mephedrone determines their effectiveness as releasers at the serotonin transporter
Mephedrone (4-methyl-N-methylcathinone) is a psychostimulant that promotes release of monoamines via the high affinity transporters for dopamine (DAT), norepinephrine (NET) and serotonin (SERT). Metabolic breakdown of mephedrone results in bioactive metabolites that act as substrate-type releasers at monoamine transporters and stereospecific metabolism of mephedrone has been reported. This study compared the effects of the enantiomers of the phase-1 metabolites nor-mephedrone, 4-hydroxytolyl-mephedrone (4-OH-mephedrone) and dihydro-mephedrone on (i) DAT, NET and SERT mediated substrate fluxes, (ii) determined their binding affinities towards a battery of monoamine receptors and (iii) examined the relative abundance of the enantiomers in human urine. Each of the enantiomers tested inhibited uptake mediated by DAT, NET and SERT. No marked differences were detected at DAT and NET. However, at SERT, the S-enantiomers of nor-mephedrone and 4-OH-mephedrone were several times more potent than the corresponding R-enantiomers. Moreover, the R-enantiomers were markedly less effective as releasers at SERT. S-nor-mephedrone displayed moderate affinities towards human alpha; 1A; , human 5-HT; 2A; and rat and mouse trace amine-associated receptor 1. These results demonstrate that stereochemistry dictates the pharmacodynamics of the phase-1 metabolites of mephedrone at SERT, but not at DAT and NET, which manifests in marked differences in their relative potencies, i.e. DAT/SERT ratios. Chiral analysis of urine samples demonstrated that nor-mephedrone predominantly exists as the S-enantiomer. Given the asymmetric abundance of the enantiomers in biological samples, these findings may add to our understanding of the subjective effects of administered mephedrone, which indicate pronounced effects on the serotonergic system
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