Characterization of ALPIDE Monolithic Active Pixel Sensor for the ALICE Inner Tracking System Upgrade Using the PS Facility at CERN

The upgrade of the Inner Tracking System (ITS), which is currently being developed by the ALICE Collaboration, aims at significantly improving the vertex and tracking resolution as well as the readout rate capabilities of the ALICE experiment at CERN. The new ITS detector will be installed during the second long LHC shutdown (LS2) in 2019-2020. It will comprise seven concentric layers of Monolithic Active Pixel Sensors (MAPS) with a total active surface of about 10m$^2$. The developed MAPS, “ALPIDE” (ALICE pixel detector), is based on the TowerJazz 180nm CMOS technology. The sensor design takes full advantage of a particular process feature, the deep p-well, which allows full CMOS circuitry within the pixel matrix, while at the same time retaining the full charge collection efficiency. A single sensor measures 15mm×30mm and contains half a million pixels distributed in 512 rows and 1024 columns. The detection efficiency of the sensors is higher than 99%, fake-hit rate is orders of magnitude lower than the required $10^-6$ pixel$^{-1}$event$^{-1}$, and the spatial resolution is within the required 5 $\mu$m over a wide range of thresholds. Sensors maintain this performance to some $10^{13}$ 1MeV $\mathrm{n_{eq}}$cm$^{-2}$ (NIEL), about 10 times the expected radiation load during the detector lifetime. The behavior of the final sensor has been investigated in a series of beam measurements and proven to completely fulfill the design requirements. In this contribution, we will present the setup used for measurements with inclined tracks. This study focuses on the results from cluster shape and the sensor efficiency analysis obtained using $\pi$ beams with 6GeV/c at the Proton Synchrotron (PS) at CERN.