This contribution describes a monolithic digital silicon photomultiplier (dSiPM), designed and characterized at DESY. It consists of an array of single photon avalanche diodes (SPADs) arranged in a 32 x 32-pixel matrix at 70 μm pitch, with embedded CMOS circuitry for on-chip signal processing. The dSiPM is designed in LFoundry’s 150-nm CMOS process employing a fully characterized SPAD design provided by the manufacturer. It enables in-pixel sensor-signal digitization and masking, and provides the full hit map and time stamping at 3-MHz frame rate with a resolution better than 100 ps. Especially the availability of highly granular position information will be beneficial for applications like the readout of scintillating fibers, or the detection of minimum-ionizing particles (MIPs). Several measurements were carried out in the laboratory and at the DESY II test-beam facility using the Caribou readout system. The dark-count rate as function of the overvoltage and temperature, the TDC resolution, as well as their differential and integral nonlinearity are presented. The dSiPM was used to identify MIPs in the test beam and has demonstrated a detection efficiency of 30 %, limited by the fill factor. Comparing the time measurements of two dSiPMs installed at the test beam, show a time resolution on the order of 50 ps.

This paper presents the design and characterization of a monolithic integrated circuit (IC) including digital silicon photomultipliers (dSiPMs) arranged in a 32$~\times~$32 pixel matrix at 70$~\mu$m pitch. The IC provides per-quadrant time stamping and hit-map readout, and is fabricated in a standard 150-nm CMOS technology. Each dSiPM pixel consists of four single-photon avalanche diodes (SPADs) sharing a quenching and subsequent processing circuitry and has a fill factor of 30$~\%$. A sub-100$~$ps precision, 12-bit time-to-digital converter (TDC) provides timestamps per quadrant with an acquisition rate of 3$~$MHz. Together with the hit map, the total sustained data throughput of the IC amounts to 4$~$Gbps. Measurements obtained in a dark, temperature-stable environment as well as by using a pulsed laser environment show the full dSiPM-IC functionality. The dark-count rate (DCR) as function of the overvoltage and temperature, the TDC resolution, differential and integral nonlinearity (DNL/INL) as well as the propagation-delay variations across the matrix are presented. With aid of additional peripheral test structures, the main building blocks are characterized and key parameters are presented.

The Large Hadron Collider at CERN will undergo an upgrade in order to increase its luminosity to 7.5 × 10 34 cm -2 s -1 . The increased luminosity during this High-Luminosity running phase, starting around 2029, means a higher rate of proton-proton interactions, hence a larger ionizing dose and particle fluence for the detectors. The current tracking system of the CMS experiment will be fully replaced in order to cope with the new operating conditions. Prototype planar pixel sensors for the CMS Inner Tracker with square 50 μm × 50 μm and rectangular 100 μm × 25 μm pixels read out by the RD53A chip were characterized in the lab and at the DESY-II testbeam facility in order to identify designs that meet the requirements of CMS during the High-Luminosity running phase. A spatial resolution of approximately 3.4 μm (2 μm) is obtained using the modules with 50 μm × 50 μm (100 μm × 25 μm) pixels at the optimal angle of incidence before irradiation. After irradiation to a 1 MeV neutron equivalent fluence of Φ eq = 5.3 × 10 15 cm -2 , a resolution of 9.4 μm is achieved at a bias voltage of 800 V using a module with 50 μm × 50 μm pixel size. All modules retain a hit efficiency in excess of 99% after irradiation to fluences up to 2.1 × 10 16 cm -2 . Further studies of the electrical properties of the modules, especially crosstalk, are also presented in this paper.

To cope with the challenging environment of the planned high luminosity upgrade of the Large Hadron Collider (HL-LHC), scheduled to start operation in 2029, CMS will replace its entire tracking system. The requirements for the tracker are largely determined by the long operation time of 10 years with an instantaneous peak luminosity of up to 7.5 x 1034 cm-2 s-1 in the ultimate performance scenario. Depending on the radial distance from the interaction point, the silicon sensors will receive a particle fluence corresponding to a non-ionising energy loss of up to ?eq = 3.5 x 1016 cm-2. This paper focuses on planar pixel sensor design and qualification up to a fluence of ?eq = 1.4 x 1016 cm-2. For the development of appropriate planar pixel sensors an R&D program was initiated, which includes n+-p sensors on 150 mm (6") wafers with an active thickness of 150 mu m with pixel sizes of 100 x 25 mu m2 and 50 x 50 mu m2 manufactured by Hamamatsu Photonics K.K. (HPK). Single chip modules with ROC4Sens and RD53A readout chips were made. Irradiation with protons and neutrons, as well was an extensive test beam campaign at DESY were carried out. This paper presents the investigation of various assemblies mainly with ROC4Sens readout chips. It demonstrates that multiple designs fulfil the requirements in terms of breakdown voltage, leakage current and efficiency. The single point resolution for 50 x 50 mu m2 pixels is measured as 4.0 mu m for non-irradiated samples, and 6.3 mu m after irradiation to ?eq = 7.2 x 1015 cm-2.

Pixelated silicon detectors are state-of-the-art technology to achieve precise tracking and vertexing at collider experiments, designed to accurately measure the hit position of incoming particles in high rate and radiation environments. The detector requirements become extremely demanding for operation at the High-Luminosity LHC, where up to 200 interactions will overlap in the same bunch crossing on top of the process of interest. Additionally, fluences up to 2.3 x 10(16) cm(-2) 1MeV neutron equivalent at 3.0 cm distance from the beam are expected for an integrated luminosity of 3000 fb(-1). In the last decades, the pixel pitch has constantly been reduced to cope with the experiments' needs of achieving higher position resolution and maintaining low pixel occupancy per channel. The spatial resolution improves with a decreased pixel size but it degrades with radiation damage. Therefore, prototype sensor modules for the upgrade of the experiments at the HL-LHC need to be tested after being irradiated. This paper describes position resolution measurements on planar prototype sensors with 100 x 25 mu m(2) pixels for the CMS Phase-2 Upgrade. It reviews the dependence of the position resolution on the relative inclination angle between the incoming particle trajectory and the sensor, the charge threshold applied by the readout chip and the bias voltage. A precision setup with three parallel planes of sensors has been used to investigate the performance of sensors irradiated to fluences up to phi(eq) = 3.6 x 10(15) cm(-2). The measurements were performed with a 5 GeV electron beam. A spatial resolution of 3.2 +/- 0.1 mu m is found for non-irradiated sensors, at the optimal angle for charge sharing. The resolution is 5.0 +/- 0.2 mu m for a proton-irradiated sensor at phi(eq) = 2.1 x 10(15) cm(-2) and a neutron-irradiated sensor at phi(eq) = 3.6 x 10(15) cm(-2). The extrapolated resolution to infinite beam momentum, where the contribution of multiple scattering can be neglected, has also been evaluated.