1,687 research outputs found
Charge carrier transfer in the gas electron multiplier at low gas gains
Connected to the Linear Collider project TESLA at DESY, studies
on the readout of TPCs based on the GEM-technology are ongoing.
For particle identication via dE/dx - measurement, a good
energy resolution is indispensable, and therefore losses of
primary electrons have to be avoided. It turned out, that in the
GEM transverse diffusion inside or close to the holes is a not
negligible reason for these losses. For Ar-CH4 90:10 and
TPC-like field configurations it was found, that when operated
in normal amplification mode, the Standard Geometry GEM should
not lose primaries, whereas for low gains, also when operated in
magnetic fields up to 5T, a GEM with larger pitch and hole
diameter would be necessary
Aging measurements with the gas electron multiplier (GEM)
Continuing previous aging measurements with detectors based on the Gas Electron Multiplier (GEM), a cm triple-GEM detector, as used in the small area tracking of the COMPASS experiment at CERN, was investigated. With a detector identical to those installed in the experiment, long-term, high-rate exposures to keV X-ray radiation were performed to study its aging properties. In standard operation conditions, with Ar:CO (70:30) filling and operated at an effective gain of , no change in gain and energy resolution is observed after collecting a total charge of 7mC/mm, corresponding to seven years of normal operation. This observation confirms previous results demonstrating the relative insensitivity of GEM detectors to aging, even when manufactured with common materials
Development and applications of the Gas Electron Multiplier
The Gas Electron Multiplier (GEM) has been recently developed to cope with the severe requirements of high luminosity particle physics experimentation. With excellent position accuracy and very high rate capability, GEM devices are robust and easy to manufacture. The possibility of cascading two or more multipliers permits to achieve larger gains and more stable operation. We discuss major performances of the new detectors, particularly in view of possible use for high rate portal imaging and medical diagnostics
Beam Performance of Tracking Detectors with Industrially Produced GEM Foils
Three Gas-Electron-Multiplier tracking detectors with an active area of 10 cm
x 10 cm and a two-dimensional, laser-etched orthogonal strip readout have been
tested extensively in particle beams at the Meson Test Beam Facility at
Fermilab. These detectors used GEM foils produced by Tech-Etch, Inc. They
showed an efficiency in excess of 95% and spatial resolution better than 70 um.
The influence of the angle of incidence of particles on efficiency and spatial
resolution was studied in detail.Comment: 8 pages, 9 figures, accepted by Nuclear Instruments and Methods in
Physics Research
Information on antiprotonic atoms and the nuclear periphery from the PS209 experiment
In the PS209 experiments at CERN two kinds of measurements were performed:
the in-beam measurement of X-rays from antiprotonic atoms and the
radiochemical, off-line determination of the yield of annihilation products
with mass number A_t -1 (less by 1 than the target mass). Both methods give
observables which allows to study the peripheral matter density composition and
distribution.Comment: LaTeX (espcrc1 style), 6 pages, 3 EPS figures, 1 table, Proceedings
of the Sixth Biennal Conference on Low-Energy Antiproton Physics LEAP 2000,
Venice, Ital
New pixelized Micromegas detector for the COMPASS experiment
New Micromegas (Micro-mesh gaseous detectors) are being developed in view of
the future physics projects planned by the COMPASS collaboration at CERN.
Several major upgrades compared to present detectors are being studied:
detectors standing five times higher luminosity with hadron beams, detection of
beam particles (flux up to a few hundred of kHz/mm^2, 10 times larger than for
the present detectors) with pixelized read-out in the central part, light and
integrated electronics, and improved robustness. Studies were done with the
present detectors moved in the beam, and two first pixelized prototypes are
being tested with muon and hadron beams in real conditions at COMPASS. We
present here this new project and report on two series of tests, with old
detectors moved into the beam and with pixelized prototypes operated in real
data taking condition with both muon and hadron beams.Comment: 11 pages, 5 figures, proceedings to the Micro-Pattern Gaseous
Detectors conference (MPGD2009), 12-15 June 2009, Kolympari, Crete, Greece
Minor details added and language corrections don
Neutron density distributions from antiprotonic 208Pb and 209Bi atoms
The X-ray cascade from antiprotonic atoms was studied for 208Pb and 209Bi.
Widths and shifts of the levels due to the strong interaction were determined.
Using modern antiproton-nucleus optical potentials the neutron densities in the
nuclear periphery were deduced. Assuming two parameter Fermi distributions
(2pF) describing the proton and neutron densities the neutron rms radii were
deduced for both nuclei. The difference of neutron and proton rms radii /\r_np
equal to 0.16 +-(0.02)_{stat} +- (0.04)_{syst} fm for 208Pb and 0.14 +-
(0.04)_{stat} +- (0.04)_{syst} fm for 209Bi were determined and the assigned
systematic errors are discussed. The /\r_np values and the deduced shapes of
the neutron distributions are compared with mean field model calculations.Comment: 22 pages, 8 tables, 15 figure
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