The ATLAS Roman Pot system is designed to determine the total proton-proton crosssection as well as the luminosity at the Large Hadron Collider (LHC) by measuring elastic proton scattering at very small angles. The system is made of four Roman Pot stations, located in the LHC tunnel in a distance of about 240 m at both sides of the ATLAS interaction point. Each station is equipped with tracking detectors, inserted in Roman Pots which approach the LHC beams vertically. The tracking detectors consist of multi-layer scintillating fibre structures readout by Multi-Anode-Photo-Multipliers.

We describe a UV photodetector with single photon (electron) counting and imaging capability. It is based on a CsI photocathode, a GEM charge multiplier and a self-triggering CMOS analog pixel chip with 105 k pixels at 50 pm pitch. The single photoelectron produced by the absorption of a UV photon is drifted to and multiplied inside a single GEM hole. The coordinates of the GEM avalanche are reconstructed with high accuracy (4 mu m rms) by the pixel chip. As a result the map of the GEM holes, arranged on a triangular pattern at 50 pm pitch, is finely imaged. (C) 2007 Published by Elsevier B.V

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lien vers le texte intégral : http://cdsweb.cern.ch/record/975366We are reporting about a scintillating fibre tracking detector which is proposed for the precise determination of the absolute luminosity of the CERN LHC at interaction point 1 where the ATLAS experiment is located. The detector needs to track protons elastically scattered under μrad angles in direct vicinity to the LHC beam. It is based on square shaped scintillating plastic fibres read out by multi-anode photomultiplier tubes and is housed in Roman Pots. We describe the design and construction of prototype detectors and the results of a beam test experiment at DESY. The excellent detector performance established in this test validates the detector design and supports the feasibility of the proposed challenging method of luminosity measurement

Aerogel with index of refraction around 1.03 has been studied as Cherenkov radiator in an experiment at the CERN PS using a π − and a mixed π + /p beam of momenta between 6 and 10 GeV/c. The Cherenkov photons were detected by means of four large HPD tubes designed and constructed at CERN. Results on the photoelectron yield, the Cherenkov angle and its resolution, and the π/p separation are obtained. The performances measured demonstrate that a RICH with aerogel is a viable detector for experiments with high multiplicity of particles in the final state.