85 research outputs found
MHSP in reversed-biased operation mode for ion blocking in gas-avalanche multipliers
We present recent results on the operation of gas-avalanche detectors
comprising a cascade of gas electron multipliers (GEMs) and Micro-Hole and
Strip Plates (MHSPs) multiplier operated in reversed-bias (R-MHSP) mode. The
operation mechanism of the R-MHSP is explained and its potential contribution
to ion-backflow (IBF) reduction is demonstrated. IBF values of 4E-3 were
obtained in cascaded R-MHSP and GEM multipliers at gains of about 1E+4, though
at the expense of reduced effective gain in the first R- MHSP multiplier in the
cascade.Comment: 23 pages, 8 figure
A concise review on THGEM detectors
We briefly review the concept and properties of the Thick GEM (THGEM); it is
a robust, high-gain gaseous electron multiplier, manufactured economically by
standard printed-circuit drilling and etching technology. Its operation and
structure resemble that of GEMs but with 5 to 20-fold expanded dimensions. The
millimeter-scale hole-size results in good electron transport and in large
avalanche-multiplication factors, e.g. reaching 10^7 in double-THGEM cascaded
single-photoelectron detectors. The multiplier's material, parameters and shape
can be application-tailored; it can operate practically in any counting gas,
including noble gases, over a pressure range spanning from 1 mbar to several
bars; its operation at cryogenic (LAr) conditions was recently demonstrated.
The high gain, sub-millimeter spatial resolution, high counting-rate
capability, good timing properties and the possibility of industrial production
capability of large-area robust detectors, pave ways towards a broad spectrum
of potential applications; some are discussed here in brief.Comment: 8 pages, 11 figures; Invited Review at INSTR08, Novosibirsk, Feb
28-March 5 200
High-gain DC-mode operated Gaseous Photomultipliers for the visible spectral range
We shortly describe recent progress in photon detectors combining bi-alkali
photocathodes and cascaded patterned gas-avalanche electron multipliers. It
permitted the development and the first feasibility demonstration of high-gain
gaseous photomultipliers sensitive in the visible spectral range, operated in
DC mode with single-photon sensitivity.Comment: Proceedings to the 5th International Conference on New Developments
In Photodetection 2008, Aix-les-Bains, France, June 15-20, 2008, submitted to
NIM
Ion-induced effects in GEM & GEM/MHSP gaseous photomultipliers for the UV and the visible spectral range
We report on the progress in the study of cascaded GEM and GEM/MHSP gas
avalanche photomultipliers operating at atmospheric pressure, with CsI and
bialkali photocathodes. They have single-photon sensitivity, ns time resolution
and good localization properties. We summarize operational aspects and results,
with the highlight of a high-gain stable gated operation of a visible-light
device. Of particular importance are the results of a recent ion-backflow
reduction study in different cascaded multipliers, affecting the detector's
stability and the photocathode's liftime. We report on the significant progress
in ion-blocking and provide first results on bialkali-photocathode aging under
gas multiplication.Comment: 6 pages, 8 figure
(E)-1-Ethyl-4-oxo-N′-(4-pyridylmethylene)-1,4-dihydroquinoline-3-carbohydrazide
In the title compound, C18H16N4O2, the plane defined by the ethyl C atoms and the attached N atom is inclined to the adjacent pyridine ring at an angle of 67.87 (16)°. The dihedral angle between the two heterocyclic rings is 3.33 (16)°. The molecular conformation is stabilized by an intramolecular N—H⋯O hydrogen bond and the crystal structure by intermolecular C—H⋯O hydrogen bonds, forming a one-dimensional structure
1-Furoyl-3-methyl-3-phenylthiourea
The title compound, C13H12N2O2S, crystallizes with two independent molecules in the asymmetric unit. The two molecules differ in the conformation of the thiocarbonyl and carbonyl groups, and show the typical geometric parameters of substituted thiourea derivatives. The crystal structure is mainly stabilized by intermolecular N—H⋯O hydrogen bonding
1-Benzyl-3-(2-furoyl)thiourea
In the title compound, C13H12N2O2S, the dihedral angle between the two aromatic ring planes is 87.52 (12)°. The molecule shows an intramolecular N—H⋯O hydrogen bond. The crystal structure is stabilized by intermolecular N—H⋯S and C—H⋯O hydrogen bonding
Charge amplification concepts for direction-sensitive dark matter detectors
Direction measurement of weakly interacting massive particles in
time-projection chambers can provide definite evidence of their existence and
help to determine their properties. This article demonstrates several concepts
for charge amplification in time-projection chambers that can be used in
direction-sensitive dark matter search experiments. We demonstrate
reconstruction of the 'head-tail' effect for nuclear recoils above 100keV, and
discuss the detector performance in the context of dark matter detection and
scaling to large detector volumes.Comment: 15 pages, 9 figure
THGEM-based detectors for sampling elements in DHCAL: laboratory and beam evaluation
We report on the results of an extensive R&D program aimed at the evaluation
of Thick-Gas Electron Multipliers (THGEM) as potential active elements for
Digital Hadron Calorimetry (DHCAL). Results are presented on efficiency, pad
multiplicity and discharge probability of a 10x10 cm2 prototype detector with 1
cm2 readout pads. The detector is comprised of single- or double-THGEM
multipliers coupled to the pad electrode either directly or via a resistive
anode. Investigations employing standard discrete electronics and the KPiX
readout system have been carried out both under laboratory conditions and with
muons and pions at the CERN RD51 test beam. For detectors having a
charge-induction gap, it has been shown that even a ~6 mm thick single-THGEM
detector reached detection efficiencies above 95%, with pad-hit multiplicity of
1.1-1.2 per event; discharge probabilities were of the order of 1e-6 - 1e-5
sparks/trigger, depending on the detector structure and gain. Preliminary beam
tests with a WELL hole-structure, closed by a resistive anode, yielded
discharge probabilities of <2e-6 for an efficiency of ~95%. Methods are
presented to reduce charge-spread and pad multiplicity with resistive anodes.
The new method showed good prospects for further evaluation of very thin
THGEM-based detectors as potential active elements for DHCAL, with competitive
performances, simplicity and robustness. Further developments are in course.Comment: 15 pages, 11 figures, MPGD2011 conference proceedin
Gaseous Dark Matter Detectors
Dark Matter detectors with directional sensitivity have the potential of
yielding an unambiguous positive observation of WIMPs as well as discriminating
between galactic Dark Matter halo models. In this article, we introduce the
motivation for directional detectors, discuss the experimental techniques that
make directional detection possible, and review the status of the experimental
effort in this field.Comment: 19 pages, review on gaseous directional dark matter detectors
submitted to New Journal of Physic
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