CMS Tracker Phase-2
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| CMS Tracker Phase-2 | |
|---|---|
| Name | CMS Tracker Phase-2 |
| Organization | CERN |
| Type | Particle detector |
CMS Tracker Phase-2
The CMS Tracker Phase-2 is the major upgrade of the Compact Muon Solenoid tracking detector for the Large Hadron Collider High-Luminosity era, intended to operate during the HL-LHC runs and to sustain the increased pileup and radiation environments foreseen by the European Strategy for Particle Physics and the Particle Physics Project Prioritization Panel. It replaces the original tracker with a new all-silicon system integrating advanced silicon sensor technologies, fast readout electronics, and upgraded trigger system interfaces to meet the physics goals set by collaborations including CMS Collaboration, ATLAS Collaboration, and other experiments at CERN.
Introduction
The Phase-2 tracker upgrade was driven by requirements from the High-Luminosity Large Hadron Collider project, informed by studies from LARP, HEPAP, and the European Laboratory for Particle Physics governance. It aims to provide hermetic tracking to high pseudorapidity, precise momentum resolution for charged particles, robust vertex reconstruction for processes explored by experiments such as ATLAS, LHCb, and ALICE, and resilience to the radiation doses comparable to those expected by 3000–4000 fb−1 integrated luminosity scenarios used in studies by the Particle Data Group and physics working groups inside the CMS Collaboration.
Design and Architecture
The architecture adopts a modular layout of concentric barrels and endcap disks informed by precedents set in upgrades of ATLAS Inner Detector, CDF Run II, and Belle II vertex systems. The design includes pixel modules arranged in multiple layers and macro-pixel or strip modules in the outer regions, with system-level choices influenced by studies from Fermilab, SLAC National Accelerator Laboratory, and DESY. Interfaces to the L1 trigger and High-Level Trigger follow specifications agreed with Trigger and Data Acquisition Group conveners, and mechanical integration plans coordinated with the CERN Engineering Department.
Silicon Sensor Technology
Silicon choices encompass planar pixel sensors, 3D sensors, and radiation-hard strip sensors drawing on R&D from IMB-CNM, Fondazione Bruno Kessler, and industrial partners such as Hamamatsu Photonics and Infineon Technologies. Sensor segmentation, pitch, and thickness are optimized based on irradiation campaigns at facilities including GIF++, TRIGA reactors, and test beams at DESY Test Beam, CERN SPS, and FNAL Test Beam Facility. Radiation tolerance goals leverage developments in CMOS MAPS sensor efforts at institutions like IPHC Strasbourg and Università di Pisa and learnings from experiments such as CMS Phase-1 Pixel Detector Upgrade and ATLAS IBL.
Readout Electronics and Data Acquisition
Front-end ASICs and fast optical links form the backbone of readout, influenced by chip designs like RD53 and by collaborations with European Organization for Nuclear Research electronics groups. The readout chain includes radiation-hard serializers, high-speed transceivers compatible with links developed for Versatile Link projects, and back-end systems using FPGA farms similar to deployments at CERN Computer Centre and collaborations with Intel, Xilinx, and Microsemi. Data-acquisition architecture integrates with the CMS Trigger system, adopting timing and control schemes compatible with Timing, Trigger and Control boards and synchronization strategies employed in ATLAS TDAQ and other large-scale detectors.
Mechanics, Cooling, and Services
Mechanical support structures and low-mass services draw on carbon-fiber composites and advanced materials investigated at CERN Materials Laboratory and partner labs including ETH Zurich and MIT. Cooling uses two-phase CO2 systems with pumps and manifolds developed in coordination with groups from University of Bristol and Imperial College London, following approaches tested in LHCb VELO and ALICE Inner Tracking System upgrades. Power distribution leverages radiation-hard DC-DC converters and serial powering schemes examined in studies at CERN and DESY, and service routing is planned to minimize material budget and enable efficient maintenance during planned accessibles defined by LS3.
Performance and Simulation Studies
Performance estimates arise from full detector simulations implemented in GEANT4 with reconstruction frameworks used by CMS Experiment, cross-checked against fast-simulation tools and benchmarking studies from Snowmass Process contributions and physics working groups. Metrics include tracking efficiency, fake-rate control in high pileup conditions, momentum and impact-parameter resolution, and b-tagging performance relevant to searches and measurements from Higgs boson physics to beyond-Standard-Model signatures explored by the CMS Collaboration and partner institutions. Validation leverages comparisons to prototypes tested at beam facilities and irradiation campaigns at facilities such as CERN ISR and PS.
Installation, Commissioning, and Operations
Installation and commissioning procedures are coordinated within the CMS integration teams and follow protocols used during LS2 and the original tracker installation, involving institutes from Universität Zürich, University of California, San Diego, Università degli Studi di Torino, and international collaborators. Commissioning includes calibration runs, alignment using track-based methods pioneered by Millepede algorithms and survey teams, and integration tests with the global CMS Detector Control System and trigger infrastructure. Operational plans anticipate tight collaboration with accelerator operation teams at CERN to manage radiation monitoring, maintenance schedules, and upgrades timed with LS3 and subsequent LHC running periods.