Silicon Wafer Fabrication and Microchannel for Cooling System in ALICE ITS

My summer student project covered details of the upgrade of Inner Tracking System (ITS) of the ALICE detector. The tasks are divided in two parts. First was on silicon wafer dicing technology and its resistivity under the supervision of Petra Riedler. Next was on silicon wafer microfabrication and cooling system in microchannel under the supervision of Andrea Francescon. ITS upgrade was proposed for better detection performance and reduction of budget. Detectors in the ITS are composed of monolithic silicon pixel chips. The thickness of the chips was proposed to be 50 μm so that particles that pass through them do not lose too much momentum. Working with very thin chips requires suitable dicing technology. Sum- mary of dicing technology is proposed for the most suitable dicing technique. Properties of the chip can be denoted by observing its resistivity. Literature reviews on surface resistivity profile measurement is represented for consideration. Cooling system is very important for the detector. Fluid that flows along microchannel cooling system is refrigerant which evaporates when its temperature rises to a certain value. Therefore, there are two phases inside the microchannel: liquid and vapour. Various two-phase flow correlations have been studied and proposed in terms of two-phase frictional pressure drop. An estimation of the two-phase pressure drop is calculated by writing a simple code in order to compare with the value from experimental data.