The distributed control system of LHC - CMS: study of the stability and dynamic range of the new SiPM detector for the HCAL

Abstract

This dissertation concerns part of the work done by the author within the CMS collaboration. It consists of seven chapters that are conceptually divided into three Parts. In the first Part the CERN Large Hadron Collider where this work has been performed is firstly 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 and 7 describe the studies performed by the author for the upgrade of the CMS Hadron Calorimeter (HCAL). An overview of the current detecting technology, the Hybrid Photo Diodes (HPD), used in the Hadron Outer Calorimeter (HO) is provided. The problems with these devices, motivating their replacement, are presented.