142 research outputs found
Operation of MHSP multipliers in high pressure pure noble-gas
We report on the performance of a Micro-Hole & Strip Plate (MHSP) electron
multiplier operating in pure Xe, Kr, Ar and Ne at the pressure range of 1 to 6
bar. The maximal gains at 1 bar Xe and Kr are 50000 and 100000, respectively;
they drop by about one order of magnitude at 2 bar and by almost another order
of magnitude at 5-6 bar; they reach gains of 500 and 4000 at 5 bar in Xe and
Kr, respectively. In Ar, the gain varies very little with pressure, being
3000-9000; in Ne the maximum attainable gain, about 100000, is pressure
independent above 2 bar. The results are compared with that of single- and
triple-GEM multipliers operated in similar conditions. Potential applications
are in hard X-ray imaging and in cryogenic radiation detectors.Comment: 16 pages, 4 figures. Submitted to JINST, 9 jan, 200
Further progress in ion back-flow reduction with patterned gaseous hole-multipliers
A new idea on electrostatic deviation and capture of back-drifting
avalanche-ions in cascaded gaseous hole-multipliers is presented. It involves a
flipped reversed-bias Micro-Hole & Strip Plate (F-R-MHSP) element, the strips
of which are facing the drift region of the multiplier. The ions, originating
from successive multiplication stages, are efficiently deviated and captured by
such electrode. Experimental results are provided comparing the ion-blocking
capability of the F-R-MHSP to that of the reversed-bias Micro-Hole & Strip
Plate (R-MHSP) and the Gas Electron Multiplier (GEM). Best ion-blocking results
in cascaded hole-multipliers were reached with a detector having the F-R-MHSP
as the first multiplication element. A three-element F-R-MHSP/GEM/MHSP cascaded
multiplier operated in atmospheric-pressure Ar/CH4 (95/5), at total gain of
~10^{5}, yielded ion back-flow fractions of 3*10^{-4} and 1.5*10^{-4}, at drift
fields of 0.5 and 0.2 kV/cm, respectively. We describe the F-R-MHSP concept and
the relevance of the obtained ion back-flow fractions to various applications;
further ideas are also discussed.Comment: 17 pages, 11 figures, published in JINS
Light multi-GEM detector for high-resolution tracking systems
Controlled etching of copper electrodes in Gas Electron Multiplier foils
allows a reduction of the material budget by more than a factor of two for a
triple-GEM detector. Detectors making use of thinned foils provide performances
similar to those obtained with standard devices: a gain above 10^4 for a
double-GEM, with energy resolution of 27 % fwhm for 5.9 keV X-rays.Comment: Submitted to Nucl.Instr.& Meth.
Performance of GEM detectors in high intensity particle beams
We describe extensive tests of Double GEM and Triple GEM detectors, including full size prototypes for the COMPASS experiment, exposed to high intensity muon, proton and pion beams at the Paul~Scherrer Institute and at CERN. The measurements aim at detecting problems possible under these operation conditions, the main concern being the occurrence of discharges induced by beam particles. Results on the dependence of the probability for induced discharges on the experimental environment are presented and discussed. Implications for the application of GEM~detectors in experiments at high luminosity colliders are illustrated
Review of the development of cesium iodide photocathodes for application to large RICH detectors
CsI photocathodes were studied in order to evaluate their potential use as large photo converters in RICH detectors for the PID system of ALICE at LHC in heavy-ion collider mode. It has been demonstrated that a quantum efficiency close to the reference value obtained on small samples can be obtained on CsI layers evaporated on large pad electrodes operated in a MWPC at atmospheric pressure. We present a survey of the results obtained in the laboratory on small samples irradiated with UV-monochromatic beams and with large area RICH detectors of proximity-focusing geometry in a 3 GeV/c pion beam
Antideuterons as a probe of primordial black holes
In most cosmological models, primordial black holes (PBHs) should have formed
in the early Universe. Their Hawking evaporation into particles could
eventually lead to the formation of antideuterium nuclei. This paper is devoted
to a first computation of this antideuteron flux. The production of these
antinuclei is studied with a simple coalescence scheme, and their propagation
in the Galaxy is treated with a well-constrained diffusion model. We compare
the resulting primary flux to the secondary background, due to the spallation
of protons on the interstellar matter. Antideuterons are shown to be a very
sensitive probe for primordial black holes in our Galaxy. The next generation
of experiments should allow investigators to significantly improve the current
upper limit, nor even provide the first evidence of the existence of
evaporating black holes.Comment: Final version, published in Astronomy & Astrophysic
A next-generation liquid xenon observatory for dark matter and neutrino physics
The nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading technology to cover the available parameter space for weakly interacting massive particles, while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector
Sensitivity projections for a dual-phase argon TPC optimized for light dark matter searches through the ionization channel
Dark matter lighter than 10  GeV/c2 encompasses a promising range of candidates. A conceptual design for a new detector, DarkSide-LowMass, is presented, based on the DarkSide-50 detector and progress toward DarkSide-20k, optimized for a low-threshold electron-counting measurement. Sensitivity to light dark matter is explored for various potential energy thresholds and background rates. These studies show that DarkSide-LowMass can achieve sensitivity to light dark matter down to the solar neutrino fog for GeV-scale masses and significant sensitivity down to 10  MeV/c2 considering the Migdal effect or interactions with electrons. Requirements for optimizing the detector’s sensitivity are explored, as are potential sensitivity gains from modeling and mitigating spurious electron backgrounds that may dominate the signal at the lowest energies
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