582 research outputs found
A triple-GEM telescope for the TOTEM experiment
The TOTEM experiment at LHC has chosen the triple Gas Electron Multiplier
(GEM) technology for its T2 telescope which will provide charged track
reconstruction in the rapidity range 5.3<|eta|<6.5 and a fully inclusive
trigger for diffractive events. GEMs are gas-filled detectors that have the
advantageous decoupling of the charge amplification structure from the charge
collection and readout structure. Furthermore, they combine good spatial
resolution with very high rate capability and a good resistance to radiation.
Results from a detailed T2 GEM simulation and from laboratory tests on a final
design detector performed at CERN are presented.Comment: To appear in the proceedings of 10th Topical Seminar on Innovative
Particle and Radiation Detectors (IPRD06), Siena, Italy, October 1-5 200
Effects of High Charge Densities in Multi-GEM Detectors
A comprehensive study, supported by systematic measurements and numerical
computations, of the intrinsic limits of multi-GEM detectors when exposed to
very high particle fluxes or operated at very large gains is presented. The
observed variations of the gain, of the ion back-flow, and of the pulse height
spectra are explained in terms of the effects of the spatial distribution of
positive ions and their movement throughout the amplification structure. The
intrinsic dynamic character of the processes involved imposes the use of a
non-standard simulation tool for the interpretation of the measurements.
Computations done with a Finite Element Analysis software reproduce the
observed behaviour of the detector. The impact of this detailed description of
the detector in extreme conditions is multiple: it clarifies some detector
behaviours already observed, it helps in defining intrinsic limits of the GEM
technology, and it suggests ways to extend them.Comment: 5 pages, 6 figures, 2015 IEEE Nuclear Science Symposiu
Charge Transfer Properties Through Graphene Layers in Gas Detectors
Graphene is a single layer of carbon atoms arranged in a honeycomb lattice
with remarkable mechanical, electrical and optical properties. For the first
time graphene layers suspended on copper meshes were installed into a gas
detector equipped with a gaseous electron multiplier. Measurements of low
energy electron and ion transfer through graphene were conducted. In this paper
we describe the sample preparation for suspended graphene layers, the testing
procedures and we discuss the preliminary results followed by a prospect of
further applications.Comment: 2014 IEEE Nuclear Science Symposium and Medical Imaging Conference
with the 21st Symposium on Room-Temperature Semiconductor X-Ray and Gamma-Ray
Detectors, 4 pages, 8 figure
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
The virtual cathode chamber
We describe the operating principle and the first experimental results obtained with gas micro-strip detectors realized with anodes only on the active side, the multiplying field being provided from the back-plane and drift electrodes. For high rate operation, the detector has to be implemented on electron conducting supports, with resistivity around 10 cm. By construction, the ³Virtual Cathode Chamber² is not subjected to the possibility of discharges between anodes and cathodes, thus avoiding one of the most dangerous problems met with standard micro-strip chambers
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
Development of large area resistive electrodes for ATLAS NSW Micromegas
Micromegas with resistive anodes will be used for the NSW upgrades of the ATLAS experiment at LHC. Resistive electrodes are used in MPGD devices to prevent sparks in high-rate operation. Large-area resistive electrodes for Micromegas have been developed using two different technologies: screen printing and carbon sputtering. The maximum resistive foil size is 45 Ă— 220 cm with a printed pattern of 425-ÎĽm pitch strips. These technologies are also suitable for mass production. Prototypes of a production model series have been successfully produced. In this paper, we report the development, the production status, and the test results of resistive Micromegas
Observation of strong wavelength-shifting in the argon-tetrafluoromethane system
We report the scintillation spectra of Ar-CF mixtures in the range
210-800~nm, obtained under X-ray irradiation for various pressures (1-5~bar)
and concentrations (0-100%). Special care was taken to eliminate effects
related to space charge and recombination, so that results can be extrapolated
following conventional wisdom to those expected for minimum ionizing particles
under the typical electric fields employed in gaseous instrumentation. Our
study sheds light into the microscopic pathways leading to scintillation in
this family of mixtures.Comment: Updated to match current journal submissio
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