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 made of ∼ 76.000 radiation hard scintillating crystals PbWO4 and operates on the Large Hadron Collider (LHC) at CERN. Almost 16.000 VFE cards that shape, amplify and digitize 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 quality assurance 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 super-modules 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 quality of the boards production and show that the CMS detector specifications are reached. (author)