Study of the mechanical support and positioning of the sensors for the new tracker of the ALICE experiment at CERN

The Inner Tracking System Detector of the ALICE Experiment at CERN laboratory will be replaced in 2020 with a new detector entirely based on pixel sensor chips. The most critical aspects in the construction of this detector are the precise positioning and the stability of the sensors over time. The work of this thesis starts with the development of a procedure for the positioning of the sensors and has been performed at INFN of Turin. The procedure is split in several steps each of them based on semi-automatic programme to control a Coordinate-Measuring Machine that position the sensors. At the end of the assembly procedure the position of the sensors is verified and recorded such to provide a detailed map. This procedure will be used in five laboratories, four in Europe and one in the United States, where the detector will be assembled. The second part of the work is focused on the mechanical design and analysis of the global support structure of the Inner Tracking System, and has been performed at CERN in close contact with the ALICE group responsible for the Mechanics and Cooling of the detector. The mechanics has to guarantee the correct position and stability of the sensors respect to the Experiment beam line. The design of these structural components is driven by tight tolerances, material minimization in the detection area and stability in time. The structure geometries and composite material layout has been optimised by using Finite Element Code. The aim of the Finite Element Analysis performed is the determination of the structures maximum deflection, due to the detector own weight, and the evaluation of the dynamic response to external vibration sources. The production and the characterisation of the prototypes, based on the results of the analysis, has permitted the final validation of the structures design.