154 research outputs found
Some operators that preserve the locality of a pseudovariety of semigroups
It is shown that if V is a local monoidal pseudovariety of semigroups, then
K(m)V, D(m)V and LI(m)V are local. Other operators of the form Z(m)(_) are
considered. In the process, results about the interplay between operators
Z(m)(_) and (_)*D_k are obtained.Comment: To appear in International Journal of Algebra and Computatio
Measurements of photoelectron extraction efficiency from CsI into mixtures of Ne with CH4, CF4, CO2 and N2
Experimental measurements of the extraction efficiency f of the UV-induced
photoelectrons emitted from a CsI photocathode into gas mixtures of Ne with
CH4, CF4, CO2 and N2 are presented; they are compared with model-simulation
results. Backscattering of low- energy photoelectrons emitted into noble gas is
significantly reduced by the admixture of molecular gases, with direct impact
on the effective quantum efficiency. Data are provided on the dependence of f
on the type and concentration of the molecular gas in the mixtures and on the
electric field.Comment: Presented at MPGD09, CRETE, June 2009; to be published in JINST
Proceeding
Development of high-gain gaseous photomultipliers for the visible spectral range
We summarize the development of visible-sensitive gaseous photomultipliers,
combining a semitransparent bi-alkali photocathode with a state-of-the-art
cascaded electron multiplier. The latter has high photoelectron collection
efficiency and a record ion blocking capability. We describe in details the
system and methods of photocathode production and characterization, their
coupling with the electron multiplier and the gaseous-photomultiplier operation
and characterization in a continuous mode. We present results on the properties
of laboratory-produced KCsSb, CsSb and NaKSb photocathodes and
report on their stability and QE in gas; KCsSb photocathodes yielded QE
values in Ar/CH(95/5) above 30% at wavelengths of 360-400 nm. The novel
gaseous photomultiplier yielded stable operation at gains of 10, in
continuous operation mode, in 700 Torr of this gas; its sensitivity to single
photons was demonstrated. Other properties are described. The successful
detection of visible light with this gas-photomultiplier pave ways towards
further development of large-area sealed imaging detectors, of flat geometry,
insensitive to magnetic fields, which might have significant impact on light
detection in numerous fields.Comment: 22 pages, 12 figures, for submission to JINS
MPGDs in Compton imaging with liquid-xenon
The interaction of radiation with liquid xenon, inducing both scintillation
and ionization signals, is of particular interest for Compton-sequences
reconstruction. We report on the development and recent results of a
liquid-xenon time-projection chamber, dedicated to a novel nuclear imaging
technique named "3 gamma imaging". In a first prototype, the scintillation is
detected by a vacuum photomultiplier tube and the charges are collected with a
MICROMEGAS structure; both are fully immersed in liquid xenon. In view of the
final large-area detector, and with the aim of minimizing dead-zones, we are
investigating a gaseous photomultiplier for recording the UV scintillation
photons. The prototype concept is presented as well as preliminary results in
liquid xenon. We also present soft x-rays test results of a gaseous
photomultiplier prototype made of a double Thick Gaseous Electron Multiplier
(THGEM) at normal temperature and pressure conditions.Comment: presented at MPGD09, CRETE, June 2009; to be published in JINST
Proceedings, PDF, 10 pages, 11 figure
Gender effect, quality of life and genetic biomarkers in a Portuguese sample with ARHL with or without tinnitus
Trabalho apresentado em Symposium & 56th Inner Ear Biology Workshop, 7-10 setembro de 2019, Pádua, ItáliaN/
Towards THGEM UV-photon detectors for RICH: on single-photon detection efficiency in Ne/CH4 and Ne/CF4
The article deals with the detection efficiency of UV-photon detectors
consisting of Thick Gas Electron Multipliers (THGEM) coated with CsI
photocathode, operated in atmospheric Ne/CH4 and Ne/CF4 mixtures. We report on
the photoelectron extraction efficiency from the photocathode into these gas
mixtures, and on the photoelectron collection efficiency into the THGEM holes.
Full collection efficiency was reached in all gases investigated, in some cases
at relatively low multiplication. High total detector gains for UV photons, in
excess of 10^5, were reached at relatively low operation voltages with a single
THGEM element. We discuss the photon detection efficiency in the context of
possible application to RICH.Comment: 13 pages, 9 figures, 1 table. Presented at MPGD09, Crete, June 2009;
to be published in JINST-proceeding
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