The SciFi Tracker

The LHCb detector finished its second run of data taking at the end of 2018. It was then upgraded during the second Long Shutdown of the LHC in 2019-2021. The main goal of the LHCb upgrade is to increase the instantaneous luminosity and the data taking rate from 1MHz to 30MHz. The previous tracking sub-systems, the inner and outer tracker positioned downstream of the LHCb dipole magnet could not support the increased occupancy and cope with the increased instantaneous luminosity. They were replaced by the SciFi tracker, composed of scintillating fibres read out by silicon photomultipliers (SiPM). The SciFi tracker consists of three stations each composed of four detection layers. In order to have an X,Y,Z measurement of the position of the particles, the second and third layers are tilted by a stereo angle of 5° with respect the y-axis. Each detection layer is composed of 12 modules which are themselves composed of 8 fibre mats. These fibre mats are 2.5m long and consist of 6 layers of 250μm fibres. The EPFL group is one of the four mat production centres and produced approximately a third of the total mats needed for the SciFi project. The group was also in charge of the development, procurement, qualification and testing of the SiPM detectors, and was heavily involved in the installation of the SciFi detector.

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