Selection of the silicon sensor thickness for the Phase-2 upgrade of the CMS Outer Tracker

During the operation of the CMS experiment at the High-Luminosity LHC the silicon sensors of the Phase-2 Outer Tracker will be exposed to radiation levels that could potentially deteriorate their performance. Previous studies had determined that planar float zone silicon with n-doped strips on a p-doped substrate was preferred over p-doped strips on an n-doped substrate. The last step in evaluating the optimal design for the mass production of about 200 m$^{2}$ of silicon sensors was to compare sensors of baseline thickness (about 300 μm) to thinned sensors (about 240 μm), which promised several benefits at high radiation levels because of the higher electric fields at the same bias voltage. This study provides a direct comparison of these two thicknesses in terms of sensor characteristics as well as charge collection and hit efficiency for fluences up to 1.5 × 10$^{15}$ n$_{eq}$/cm$^{2}$. The measurement results demonstrate that sensors with about 300 μm thickness will ensure excellent tracking performance even at the highest considered fluence levels expected for the Phase-2 Outer Tracker

Beam test performance of a prototype module with Short Strip ASICs for the CMS HL-LHC tracker upgrade

The Short Strip ASIC (SSA) is one of the four front-end chips designed for the upgrade of the CMS Outer Tracker for the High Luminosity LHC. Together with the Macro-Pixel ASIC (MPA) it will instrument modules containing a strip and a macro-pixel sensor stacked on top of each other. The SSA provides both full readout of the strip hit information when triggered, and, together with the MPA, correlated clusters called stubs from the two sensors for use by the CMS Level-1 (L1) trigger system. Results from the first prototype module consisting of a sensor and two SSA chips are presented. The prototype module has been characterized at the Fermilab Test Beam Facility using a 120 GeV proton beam

Test beam performance of a CBC3-based mini-module for the Phase-2 CMS Outer Tracker before and after neutron irradiation

The Large Hadron Collider (LHC) at CERN will undergo major upgrades to increase the instantaneous luminosity up to 5–7.5×10$^{34}$ cm$^{-2}$s$^{-1}$. This High Luminosity upgrade of the LHC (HL-LHC) will deliver a total of 3000–4000 fb-1 of proton-proton collisions at a center-of-mass energy of 13–14 TeV. To cope with these challenging environmental conditions, the strip tracker of the CMS experiment will be upgraded using modules with two closely-spaced silicon sensors to provide information to include tracking in the Level-1 trigger selection. This paper describes the performance, in a test beam experiment, of the first prototype module based on the final version of the CMS Binary Chip front-end ASIC before and after the module was irradiated with neutrons. Results demonstrate that the prototype module satisfies the requirements, providing efficient tracking information, after being irradiated with a total fluence comparable to the one expected through the lifetime of the experiment

Selection of the silicon sensor thickness for the Phase-2 upgrade of the CMS Outer Tracker

During the operation of the CMS experiment at the High-Luminosity LHC the silicon sensors of the Phase-2 Outer Tracker will be exposed to radiation levels that could potentially deteriorate their performance. Previous studies had determined that planar float zone silicon with n-doped strips on a p-doped substrate was preferred over p-doped strips on an n-doped substrate. The last step in evaluating the optimal design for the mass production of about 200 m2 of silicon sensors was to compare sensors of baseline thickness (about 300 μm) to thinned sensors (about 240 μm), which promised several benefits at high radiation levels because of the higher electric fields at the same bias voltage. This study provides a direct comparison of these two thicknesses in terms of sensor characteristics as well as charge collection and hit efficiency for fluences up to 1.5 × 1015 neq/cm2. The measurement results demonstrate that sensors with about 300 μm thickness will ensure excellent tracking performance even at the highest considered fluence levels expected for the Phase-2 Outer Tracker

Selection of the silicon sensor thickness for the Phase-2 upgrade of the CMS Outer Tracker

International audienceDuring the operation of the CMS experiment at theHigh-Luminosity LHC the silicon sensors of the Phase-2 Outer Trackerwill be exposed to radiation levels that could potentiallydeteriorate their performance. Previous studies had determined thatplanar float zone silicon with n-doped strips on a p-doped substratewas preferred over p-doped strips on an n-doped substrate. The laststep in evaluating the optimal design for the mass production ofabout 200 m$^{2}$ of silicon sensors was to compare sensors ofbaseline thickness (about 300 μm) to thinned sensors (about240 μm), which promised several benefits at high radiationlevels because of the higher electric fields at the same biasvoltage. This study provides a direct comparison of these twothicknesses in terms of sensor characteristics as well as chargecollection and hit efficiency for fluences up to1.5 × 10$^{15}$ n$_{eq}$/cm$^{2}$. The measurement resultsdemonstrate that sensors with about 300 μm thickness willensure excellent tracking performance even at the highest consideredfluence levels expected for the Phase-2 OuterTracker

Evaluation of planar silicon pixel sensors with the RD53A readout chip for the Phase-2 Upgrade of the CMS Inner Tracker

The Large Hadron Collider (LHC) at CERN will undergo an upgrade in order to increase its luminosity to $7.5 \times 10^{34}$ cm$^{-2}$s$^{-1}$. The increased luminosity during this High-Luminosity running phase\\ (HL-LHC), 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 $50 \mu$m $\times \; 50 \mu$m and rectangular $100 \mu$m $\times \; 25 \mu$m 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 at the HL-LHC. A spatial resolution of approximately 3.4$\mu$m (2$\mu$m) is obtained using the modules with $50 \mu$m $\times \; 50 \mu$m ($100 \mu$m $\times \; 25 \mu$m) pixels at the optimal angle of incidence before irradiation. After irradiation to a 1 MeV neutron equivalent fluence of $\Phi_{\rm eq} = 5.3 \times 10^{15}$ cm$^{-2}$, a resolution of 9.4$\mu$m is achieved at a bias voltage of 800 V using a module with $50 \mu$m $\times \; 50 \mu$m pixel size. All modules retain a hit efficiency in excess of 99\% after irradiation to fluences up to $2.1 \times 10^{16}$ cm$^{-2}$. Further studies of the electrical properties of the modules, especially crosstalk, are also presented in this paper.The Large Hadron Collider at CERN will undergo an upgrade inorder to increase its luminosity to7.5 × 10$^{34}$ cm$^{-2}$s$^{-1}$. The increased luminosityduring this High-Luminosity running phase, starting around 2029,means a higher rate of proton-proton interactions, hence a largerionizing dose and particle fluence for the detectors. The currenttracking system of the CMS experiment will be fully replaced inorder to cope with the new operating conditions. Prototype planarpixel sensors for the CMS Inner Tracker with square50 μm × 50 μm and rectangular100 μm × 25 μm pixels read out by theRD53A chip were characterized in the lab and at the DESY-II testbeamfacility in order to identify designs that meet the requirements ofCMS during the High-Luminosity running phase. A spatial resolutionof approximately 3.4 μm (2 μm) is obtained using themodules with 50 μm × 50 μm(100 μm × 25 μm) pixels at the optimalangle of incidence before irradiation. After irradiation to a 1 MeVneutron equivalent fluence ofΦ$_{eq}$ = 5.3 × 10$^{15}$ cm$^{-2}$, a resolution of9.4 μm is achieved at a bias voltage of 800 V using a modulewith 50 μm × 50 μm pixel size. All modulesretain a hit efficiency in excess of 99% after irradiation tofluences up to 2.1 × 10$^{16}$ cm$^{-2}$. Further studies ofthe electrical properties of the modules, especially crosstalk, arealso presented in this paper.The Large Hadron Collider (LHC) at CERN will undergo an upgrade in order to increase its luminosity to $7.5 \times 10^{34}$ cm$^{-2}$s$^{-1}$. The increased luminosity during this High-Luminosity running phase (HL-LHC), 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 $50 \mu$m $\times \; 50 \mu$m and rectangular $100 \mu$m $\times \; 25 \mu$m 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 at the HL-LHC. A spatial resolution of approximately 3.4$\mu$m (2$\mu$m) is obtained using the modules with $50 \mu$m $\times \; 50 \mu$m ($100 \mu$m $\times \; 25 \mu$m) pixels at the optimal angle of incidence before irradiation. After irradiation to a 1 MeV neutron equivalent fluence of $\Phi_{\rm eq} = 5.3 \times 10^{15}$ cm$^{-2}$, a resolution of 9.4$\mu$m is achieved at a bias voltage of 800 V using a module with $50 \mu$m $\times \; 50 \mu$m pixel size. All modules retain a hit efficiency in excess of 99% after irradiation to fluences up to $2.1 \times 10^{16}$ cm$^{-2}$. Further studies of the electrical properties of the modules, especially crosstalk, are also presented in this paper