TCAD simulations of pixel sensors for the ATLAS ITk upgrade and performance of annealed planar pixel modules

Abstract

A: For the high luminosity phase of the Large Hadron Collider to start operation around 2026, a major upgrade of the ATLAS Inner Tracker (ITk) is in preparation. Thanks to their low power dissipation and high charge-collection efficiency after irradiation, thin planar pixel modules are the baseline option to instrument all, except for the innermost layer of the pixel detector. To optimise the sensor layout for a pixel cell size of 50 × 50 µm 2 , TCAD simulations are being performed. Charge-collection efficiency, electronic noise and electrical-field properties are investigated. A radiation-damage model is employed in TCAD simulations to estimate the performance before-and after irradiation. The impact of storage time at room temperature for the ITk pixel detector during maintenance periods are estimated using sensors irradiated up to a fluence of 5×10 15 n eq /cm 2 . Pixel sensors of 100 − 150 µm thickness, interconnected to FE-I4 read-out chips with pixel dimensions of 50 × 250 µm 2 , are characterised using the testbeam facilities at the CERN-SPS and DESY. The charge-collection and hit efficiencies are compared before and after annealing at room temperature for up to one year.