Recent results of the ATLAS upgrade Planar Pixel Sensors R&D project

Abstract

To extend the physics reach of the LHC, upgrades to the accelerator are planned which will increase the integrated annual luminosity by a factor of 5–10. This will increase the occupancy and the radiation damage of the inner trackers. To cope with the elevated occupancy, the ATLAS experiment plans to introduce an all silicon inner tracker for High Luminosity LHC (HL-LHC) operation. With silicon, the occupancy can be adjusted by using the appropriate pitch for the pixels/micro-strips. Constraints due to high radiation damage mean that only sensors with electrode configuration designed to read out the electron signal (n-in-p and n-in-n) are considered. To investigate the suitability of planar pixel sensors (PPS) for the ATLAS tracker upgrade, a dedicated R&D project was established, with 17 institutes and more than 80 scientists. The main focuses of research are the performance of planar pixel sensors after the high fluences expected during HL-LHC operation, the optimisation of the detector and module production technologies for cost reduction to enable the instrumentation of large volumes and the reduction of the inactive areas needed for electrical insulation of the sensitive region from the cut edge of the sensors. An overview of recent accomplishments of the PPS (Planar Pixel Sensors) R&D project is given. The performance in terms of charge collection and tracking efficiency, evaluated with radioactive sources in the laboratory and from beam tests, is presented. Sensors with different thicknesses (ranging from 75 to 300μm) were irradiated to several fluences up to 2×1016neqcm−2 to study the effect of varying thickness on the radiation hardness. The significant progresses made towards the reduction of the edge distance are reported.