The distributed control system of LHC-CMSstudy of the stability and dynamic range of the new sipm detector for the HCAL

Resumo

This dissertation recapitulates the work done by the author within the CMS collaboration. It consists of nine Chapters that are conceptually divided into three Parts. The first Part includes the Introduction and the first two Chapters. Firstly the CERN Large Hadron Collider where this work has been performed is described. The overall CMS detector is then presented: the sub-detectors and main systems are described, providing also an overview of the collaboration organization, as well as the experimental infrastructure. Finishing Part I, the main purpose of the CMS Detector Control System (DCS) is summarized together with the technologies chosen to cope with its operational, functional, environmental and organizational requirements. The main contributions of the author of this thesis to this first part consisted in the selection, validation and development of technologies and tools for the implementation of the CMS DCS. Part II includes Chapters 3, 4 and 5, and focuses on the developments performed in several sub-systems of the CMS DCS. The development challenges of the DCS and its unique infrastructure are brought to light. The overall design and architecture, with its different layers, is presented. Chapter 4 is dedicated to the operational aspects. The detector protection and the automation mechanisms are presented. Then, a practical example of a sub-detector control system is presented in Chapter 5. The architecture and development details of the CMS Electromagnetic Calorimeter (ECAL) supervisory control and its different control subsystems are explained. The author of this thesis participated in the design of the overall architecture of the DCS and in the definition of the operational model of the detector. Furthermore, the author of this thesis closely worked with the different CMS sub-detectors to assist them during the implementation of their local control system. An example of this is the implementation of the ECAL DCS where the author was a key developer of the system. The author also proposed and implemented various protection mechanisms that are currently in use at CMS. Finally, in Part III, Chapters 6, 7 and 8 are dedicated to the studies performed by the author for the upgrade of the CMS Hadron Calorimeter (HCAL). A brief introduction on hadron calorimetry is followed by an overview of the Outer Hadron Calorimeter (HO) and its initial detecting technology, the Hybrid Photo Diodes (HPD). The problems with these devices, motivating their replacement, are presented. Chapter 7 presents a photo detection technology based on Silicon Photomultipliers (SiPM), intended to replace the HPD in the HO calorimeter and it summarizes the work done to validate and characterize these devices. The test bench in an integration area at CERN is described, and the stability studies performed are discussed. Chapter 8 presents the analysis of the data acquired during a test beam, devoted to validate the use of the SiPM in the HO sub-detector. The author of this thesis developed the control system to perform these studies. Moreover, he participated in the data-taking and in the analysis for both the characterization of the SiMP detectors at the test-bench and various experimental setups to study the detector response to particles. The results of the SiPMs dynamic range studies are compared to the results with HPDs. In addition, the effects of using light mixers in front of the photo-detector devices are also presented. The chapter concludes providing a suggestion for an optimal configuration for the operation of the SiPMs in HO and discussing the impact of the DCS controlled parameters on the performance of the calorimeter to the physics processes of interest at the LHC.