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Multipoint position monitoring optical systems for ALICE and ATLAS experiments at CERN

Ziel

The objective of the Project is to develop and create for the Dimuons Forward Spectrometer (DFS) of ALICE and for Muon Spectrometer (MS) of ATLAS experiments at CERN the multipoint position monitoring optical systems (MPMOS) which provide high-precision (with a resolution of a few tens mm) control of the relative positioning and deformations of the muon tracking chambers entering the spectrometers. The main aim of ALICE is to discover Quark-Gluon Plasma, while the primary goal of ATLAS is to find Higgs boson. These tasks call for the detection of muons and high-resolution measurement of their momenta in a large interval from 1 to 1000GeV. The DFS and MS represent very complex and large (with dimensions extending up to 20 m) setups consisting of numerous tracking chambers. Because of large dimensions, the geometry of spectrometers cannot be fixed mechanically at requested accuracy of a few tens microns. Instead, the movements of the chambers during the experimental data taking will be registered by specially designed monitoring systems and the corrections will be introduced in the offline analysis. The project is dedicated to the R&D and creation of the software and hardware elements of the MPMOS. The latter represents a set of optical/laser beams, which serves as a reference frame for the measurement of the chamber movements. Each beam passes through a chain of = 3 semitransparent sensors (straightness monitors) which are fixed on the chambers and which measure the optical beam position with an accuracy of a few µm.

The research activities consist of the following Tasks:
T1 - Monte Carlo simulations of the conceptual scheme of the monitoring system in DFS (study of the optimum number of the beams, the position of sensors and collimators, the installation tolerances for the chambers and optical elements, the requirements to the intrinsic resolution of the sensors);
T2 and T3 - R&D, manufacturing and test work on two straightness monitors. One of them, called ALMY, was developed by Munich group, while the second monitor, called RELMY, has been suggested by Yerevan-YerPhI team. The work on ALMY silicon strip sensor (providing the beam spot position measurement with a resolution of 5 mm) consists in equipping it with new, PC-compatible readout electronics, suggested by Minich and YerPhI groups. The project foresees further development, integration with the readout electronics and numerous tests of RELMY monitor where the position of the beam is determined by the currents from photodiodes exposed to the reflected image of the beam. The actual prototype of RELMY measures the beam position with a resolution of 5 mm;
T4 - R&D for the optical beam reference system which includes the collimated and protected laser beams with the profile sizes optimised taking into account the resolution of the sensors and the monitoring distances;
T5 - Design and manufacture of the mechanical components of MPMOS, including micropositioning and support devices for the sensors and collimators. Engineering study and performance of the high-accuracy survey/fixation of the reference optical beam system in the ALICE overall coordinate frame;
T6 - Test and final optimisation of the monitoring systems using the CERN's DATCHA test detector and cosmic muons.
As a result of the work on the project realisation, it is expected to create technological and engineering products (semitransparent sensors, laser beam distribution system, micropositioning mechanics) and to apply them to the experimental purposes of the high-resolution measurements of the muon characteristics (momenta, dimuon and four-muon invariant masses) in the ALICE and ATLAS experiments.

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Koordinator

Max-Planck-Gesellschaft
EU-Beitrag
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Adresse
Foehringer Ring 6
80805 München
Deutschland

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Beteiligte (3)