Speaker
Description
The CMS Phase-2 Outer Tracker is progressing toward large-scale system validation ahead of LS3 installation. Multi-module mechanical structures— ladders, rings, planks, and dees— assembled and characterized at integration centers, are brought together into higher-level structures and tested at the Tracker Integration Facility at CERN with final services and complete readout architecture. Noise performance and electrical interactions between integrated sub-components are characterized as system complexity grows. The full DAQ chain, based on DTC boards and the ShepHerdRunControl framework, is being commissioned to validate scalability, throughput, and control. Latest results from these system-level integration activities and the path toward LS3 are presented.
Summary (500 words)
The CMS Phase-2 Outer Tracker is progressing toward large-scale system validation ahead of LS3 installation. The detector comprises two module types: 2S modules, hosting two strip sensors read out by CBC ASICs, and PS modules, combining a pixel and a strip sensor read out by MPA and SSA ASICs respectively. Mechanical substructures such as ladders, rings, planks, and dees — each hosting modules extensively characterized at assembly centers — are being assembled. Modules integration centers perform the assembly and operation of these multi-module structures, verifying communication integrity, noise studies, and powering-chain performance under controlled conditions. These validated elements are then assembled into higher-level structures — wheel, stacked rings, layers of planks for the barrel and double-disks of dees for the endcaps — which will be tested at CERN at the Tracker Integration Facility (TIF). There, they will be tested with the final services, and with the complete readout architecture. The programme concentrates on electrical commissioning, large-scale data flow, and system stability, providing the first opportunity to exercise the detector in configurations approaching those of the final installation. The readout is based on the Data, Trigger, and Control (DTC) board, built on the Serenity ATCA platform and hosting a Xilinx Zynq UltraScale+ MPSoC. The Zynq integrates ARM processing cores alongside programmable logic fabric on a single device, requiring careful co-design of firmware and software to correctly manage shared resources between the two domains. Front-end communication is handled through the EMP framework, a standardized CMS infrastructure providing common firmware — together with corresponding control and monitoring software — to support arbitrary user payload firmware running on FPGA-based readout boards. Each DTC serves up to 72 modules, and a central goal of commissioning is verifying that it can autonomously calibrate all attached front-end components — a property that makes scaling to multi-DTC operation, required to instrument the full tracker of over 10,000 modules, straightforward by replication rather than complex coordination. The calibration logic is implemented in tk-fe-daq, a dedicated library that centralises detector state transitions, front-end calibration procedures, and firmware interaction via EMP, providing a coherent and reproducible interface through which the detector is brought from initialization to fully calibrated operation. As the system under test grows in complexity — from a single module to a full multi-module structure — tk-fe-daq ensures this progression is handled consistently. The ShepHerd's Crook framework, jointly developed by the L1T and Tracker communities, then extends this to the multi-DTC domain: providing hierarchical run control from a global tracker-wide instance, through per-subsystem supervisors, down to on-board controllers running directly on each DTC and loading hardware-specific plugins at runtime.