Upgrading the ATLAS Silicon Tracking for the HL-LHC

After successful operation of the LHC at a centre-of-mass energy of 8 TeV this year, the energy is expected to go up to 14 TeV in the next few years. A total integrated luminosity of 300 fb-1 foreseen to be reached by 2020. At that time, the LHC will undergo a major upgrade to the High Luminosity LHC (HL-LHC), which is designed to deliver of order five times the LHC nominal instantaneous luminosity along with luminosity leveling. The final goal is to extend the data set to 3000 fb-1 by around 2030. Current planning in ATLAS involves significant upgrades to the detector during the consolidation of the LHC to reach full LHC energy and further upgrades to accommodate running already beyond nominal luminosity this decade. The challenge of coping with HL-LHC instantaneous and integrated luminosity, along with the associated radiation levels, requires further major changes to the ATLAS detector. The designs are developing rapidly for an all-new inner-tracker, significant upgrades in the calorimeter and muon systems, as well as improved triggers and data acquisition. This presentation concentrates on the HL-LHC upgrade of the ATLAS Inner Tracker (ITK), which consist of replacing the entire current Inner Detector (silicon pixels, silicon strips and transition radiation tracker) with a completely new silicon-only system. This new ITK will be made from several pixel and strip layers, and is designed to withstand the extreme radiation environment in close proximity to the HL-LHC interaction point which broadly speaking means an order of magnitude higher radiation hardness than the existing ID. At the same time, the radiation length should be kept to the level of the present system or below. In the current planning, the pixel system involves 4 barrel layers and 6 disks on each side for a total pixel area of 7m2 and 400 million channels. The strip system will contain 5 barrel layers and 5 end-cap disks, covering 200m2 of silicon and 45 million channels.