Recent results of the ATLAS upgrade planar pixel sensors R&D project

Abstract

To extend the physics reach of the LHC experiments, several upgrades to the accelerator complex are planned, culminating in the HL-LHC, which eventually leads to an increase of the peak luminosity by a factor of five to ten compared to the LHC design value.To cope with the higher occupancy and radiation damage also the LHC experiments will be upgraded. The ATLAS Planar Pixel Sensor R&D Project is an international collaboration of 17 institutions and more than 80 scientists, exploring the feasibility of employing planar pixel sensors for this scenario.Depending on the radius, different pixel concepts are investigated using laboratory and beam test measurements. At small radii the extreme radiation environment and strong space constraints are addressed with very thin pixel sensors active thickness in the range of (75–150)μm, and the development of slim as well as active edges. At larger radii the main challenge is the cost reduction to allow for instrumenting the large area of (7–10)m2. To reach this goal the pixel productions are being transferred to 6in production lines and more cost-efficient and industrialised interconnection techniques are investigated. Additionally, the n-in-p technology is employed, which requires less production steps since it relies on a single-sided process.An overview of the recent accomplishments obtained within the ATLAS Planar Pixel Sensor R&D Project is given. The performance in terms of charge collection and tracking efficiency, obtained with radioactive sources in the laboratory and at beam tests, is presented for devices built from sensors of different vendors connected to either the present ATLAS read-out chip FE-I3 or the new Insertable B-Layer read-out chip FE-I4. The devices, with a thickness varying between 75μm and 300μm, were irradiated to several fluences up to 2×1016neq/cm2. Finally, the different approaches followed inside the collaboration to achieve slim or active edges for planar pixel sensors are presented.