W. Cameron

THE NEW ALEPH SILICON VERTEX DETECTOR

The ALEPH collaboration, in view of the importance of effective vertex detection for the Higgs boson search at LEP 2, decided to upgrade the previous vertex detector. Main changes were an increased length (+/- 20 cm), a higher granularity for r phi view (50 mu m), a new preamplifier (MX7 rad hard chip), a polymide (upilex) fan-out on z side to carry the signals from the strips to the front-end electronics outside the fiducial region reducing consequently the passive material in the central region by a factor of two. The detector, the running experience and its performance will be described

Studies of Lead Tungstate Crystal Matrices in High-Energy Beams for the CMS Electromagnetic Calorimeter at the LHC

Using matrices of lead tungstate crystals, energy resolutions better than 0.6% at 100 GeV have been achieved in the test beam in 1995. It has been demonstrated that a lead tungstate electromagnetic calorimeter read out by avalanche photodiodes can consistently achieve the excellent energy resolutions necessary to justify its construction in the CMS detector. The performance achieved has been understood in terms of the properties of the crystals and photodetectors.

Results from tests on matrices of lead tungstate crystals using high energy beams

The performance of lead tungstate crystals using photomultipliers and Si avalanche photodiodes to detect the scintillation light has been studied using high energy electron, pion and muon beams at CERN. Results from tests carried out in 1993 and 1994 are presented. Good energy resolution has been obtained using photomultipliers. Some further development is required of crystals and avalanche photodiodes in order to achieve a performance, with avalanche photodiode readout, similar to that obtained using photomultipliers.

Performance of the three-dimensional readout of the ALEPH inner tracking chamber

Abstract The Inner Tracking Chamber provides three-dimensional coordinates of hits for the ALEPH tracking system. It can also find three dimensional trajectories as part of the level 1 trigger decision. The performance of these functions is discussed.

The Magnetic Distortion Calibration System of the LHCb RICH1 Detector

The LHCb RICH1 detector uses hybrid photon detectors (HPDs) as its optical sensors. A calibration system has been constructed to provide corrections for distortions that are primarily due to external magnetic fields. We describe here the system design, construction, operation and performance.

Construction and testing of a precision 2 m long straw chamber prototype

Abstract The construction and testing of a 2 m straw chamber prototype is described. We achieved straw alignment of better than 30 μm and wire alignment of order 7 μm while keeping the amount of material to about one half the amount normally needed for a similar all-wire drift chamber.

The new slow control system for the ALEPH experiment at LEP

Abstract The ALEPH slow control system consists of 7000 channels distributed over 35 networked microprocessors which are used to control and monitor the experimental apparatus. To improve the performance, the readout has been upgraded from a ROM based system to use 3U VME processors, running OS9. A new object- oriented design for the software has been implemented, where the full description of the system is held centrally in a relational database on the host VAX cluster. Control and monitoring is carried out through a library, which accesses the database and handles communications with the processors over Ethernet using a client-server model. The design and implementation of the system and initial experience with its use are described.