Recent achievements of the ATLAS upgrade Planar Pixel Sensors R&D Project

Abstract

After the foreseen upgrade of the LHC towards the HL-LHC, coming along with higher beam energies and increased peak luminosities, the experiments have to upgrade their detector systems to cope with the expected higher occupancies and radiation damages. In case of the ATLAS experiment a new Inner Tracker will be installed in this context. The ATLAS Planar Pixel Sensor R&D Project (PPS) is investigating the possibilities to cope with these new requirements, using planar pixel silicon sensors, working in a collaboration of 17 institutions and more than 80 scientists. Since the new Inner Tracker is supposed to have an active area on the order of 8 m(2) on the one side and has to withstand extreme irradiation on the other side, the PPS community is working on several approaches to reduce production costs, while increasing the radiation tolerance of the sensors. Another challenge is to produce sensors in such large quantities. During the production of the Insertable b-Layer (IBL) modules, the PPS community has proven to be able to produce a large scale production of planar silicon sensors with a high yield. For cost reduction reasons, it is desirable to produce larger sensors. There the PPS community is working on so called quad-and hex-modules, which have a size of four, respectively six FE-I4 readout chips. To cope with smaller radii and strict material budget requirements for the new pixel layers, developments towards sensors with small inactive areas are in the focus of research. Different production techniques, which even allow the production of sensors with active edges, have been investigated and the designs were qualified using lab and testbeam measurements. The short distance between the new innermost pixel layers and the interaction point, combined with the increase in luminosity, requires designs which are more radiation tolerant. Since charge collection on the one hand decreases with irradiation and on the other hand is not uniform within the pixel cells, design modifications of the pixel implantations are under investigation. The latest achievements of these topics are presented in this paper.