Test beam results on 3D pixel sensors for the CMS Tracker upgrade at the High-Luminosity LHC

Abstract

The High Luminosity upgrade of the CERN Large Hadron Collider (HL-LHC) requires new high-radiation tolerant silicon pixel sensors for the innermost part of the tracking detector in the CMS experiment. The innermost layer of the tracker, which is as close $\mathrm{3\, cm}$ from the interaction point, will be exposed to a fluence of $\mathrm{3.4\times10^{16}\, n_{eq} cm^{-2}}$ during the high-luminosity operation period. The 3D pixel sensor technology has been proven to be the best option for such a layer in terms of radiation tolerance and low power consumption. An extensive program aiming at 3D pixel sensors has been carried out in the context of the CMS tracker R\&D activities. The sensors have been produced by Fondazione Bruno Kessler (Trento, Italy) and Centro Nacional de Microelectrónica (Barcelona, Spain). They are connected with the CROCv1 readout chip, which is a prototype of the final version. The modules have been tested in beams at CERN and DESY, before and after irradiation up to an equivalent fluence of about $\mathrm{1.6\times10^{16}\, n_{eq} cm^{-2}}$. An overview of the results obtained in the latest beam test experiments is presented, including hit detection efficiency and spatial resolution. The analysis of collected data shows excellent performance, with around 98\% hit detection efficiencies measured after irradiation.