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Fiche détaillée Thèses
Université Claude Bernard - Lyon I (20/05/2008), Houmani El Mamouni; M. Finger (Dir.)
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Calibration et études des performances de l'électronique frontale du calorimètre électromagnétique de l'expérience CMS auprès du collisionneur LHC
Jan Blaha1

L'électronique frontale (VFE) traitant les signaux des photodétecteurs du calorimètre électromagnétique de l'expérience CMS a été soumise à un programme étendu de tests pour garantir leur fonctionnalité et fiabilité. Le système de calibration et de caractérisation précise des ~16000 VFE a été développé et utilisé à IPN Lyon pour contrôler leur qualité et mesurer les constantes de calibration qui serviront au démarrage du calorimètre complet.
En outre, l'évaluation et l'optimisation précises des performances de l'électronique de lecture ont été obtenues avec des données réelles au cours de tests sur des faisceaux de particules au CERN.
Les résultats obtenus sur bancs de tests en laboratoire ou en faisceau confirment l'excellente qualité de la production des cartes électroniques et prouvent que les spécifications du calorimètre ont été atteintes.
1 :  IPNL - Institut de Physique Nucléaire de Lyon
LHC – CMS – ECAL – VFE – calibration – Higgs boson – calorimeter

Calibration and performance test of the Very-Front-End electronics for the CMS electromagnetic calorimeter
A Very-Front-End (VFE) card is an important part of the on-detector read-out electronics of the CMS (Compact Muon Solenoid) electromagnetic calorimeter that is built of ~76,000 radiation hard scintillating crystals PbWO4 and operates on the Large Hadron Collider (LHC) at CERN. Almost 16,000 VFE cards which shape, amplify and digitalize incoming signals from photodetectors generated by interacting particles. Since any maintenance of any part of the calorimeter is not possible during the 10-year lifetime
of the experiment, the extensive screening program was employed throughout the whole manufacture process. As a part of readout electronics QA program, the systems for burn-in and precise calibration of the VFE boards were developed and successfully used at IPN Lyon. In addition to functionality tests, all relevant electrical properties of each card were measured and analyzed in detail to obtain their full characterization and to build a database with all required parameters which will serve for the initial calibration of the whole calorimeter. In order to evaluate the calorimeter performance and also to deliver the most precise calibration constants, several fully equipped supermodules were extensively studied and calibrated during the test beam campaigns at CERN. As an important part of these tests, accurate studies of the electronics noise and relative gains, which are needed for measurement in high energy range, were carried out to optimize amplitude reconstruction procedure and thus improve the precision of the calorimeter energy determination. The heart of the thesis consists of the calibration of all VFE boards, including optimization of the laboratory calibration system and precise analysis of measured values to delivered desired calibration constants. The second half of the thesis is focused on the accurate evaluation and optimization of the read-out electronics in real data taking conditions. The results obtained in the laboratory at IPN Lyon as well as during test beam at CERN confirm the high of the boards production and show that the CMS detector specifications are reached.

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