The ePIC Silicon Vertex Tracker IB-OB: design and thermal-mechanical simulations

Outlook •MOSAIX: Tests of MOSAIX sensors more ePIC-oriented (timing, fake hit rate). •Mechanical and thermal load simulation: Implementation of design details and crosscheck of FEA on mock-up and first prototype with dummy thermal load. •Mechanical support: Definition of materials and of design parameters to match required performances of mechanical stability and material budget. Production of prototypes at end of the 2025. Inner Barrel •Stave Tests: Continue the quarter-staves production including I-beam and K9 foam blocks and start of flow tests. Update drawings for remaining mold parts for full stave & manufacture. •Vibrational Tests: Test quarter length stave on vibration table to compare with FEA. •Mechanical Tests: Measure stave deformation with heat generation and internal pressure. •Thermal Tests: Study temperature with air flow adding dummy ancillary ASIC. Outer Barrel Outer Barrel The ANSYS Modal model is performed on a cantilevered (diving board) quarter-stave without sensors: the FEA gives a frequency of 97 Hz for the first mode. This configuration gives similar magnitude frequencies of a fully supported L4 stave. Vibrational FEA High Stiffness end support The Outer Barrel (OB) is designed to provide high precision position measurements with large lever arm to deliver the required momentum resolution and acceptance at intermediate pseudorapidity. OB is composed by two active layers L3/L4, each segmented in staves assembled into a tiled/turbine like barrel structure. L3 and L4 will have four and two modules per facing respectively, for a material budget of 0.55% X/X0 and 0.25% X/X0. The OB will be equipped with a modified version of the ALICE ITS3 sensor called the EIC Large Area Sensor (LAS), thinned down to 50 µm and optimized for high yield, low cost, and large area coverage. Quarter-stave prototype (left), stave structure (middle) and OB design (right). quarter stave end outer facing inner facing OB structure Two L4 quarter staves prototypes have been produced, comprehensive of the carbon fiber top/bottom skins, pure Kapton FPC mock-ups and SLA 3D printed stave end supports. They show no noticeable twists, but reinforcements will be needed to avoid supports end deformation. Mechanical FEA and Test Picture of three-point bending test (left) and FEA with 0.981 N vertical load (right) The prototypes have been tested with a three-point bending test. The deformation of the center is measured as a function of the load placed upon it. The comparison plot is shown on the left: the results (blue dot) and FEA (orange line) are in good agreement. Silicon Vertex Tracker The SVT is composed of the Inner Barrel (IB), the Outer Barrel (OB), covering the central pseudorapidity range, and the two groups of endcap disks (not discussed here), for a total active area of approximately 8.5 m2. The role of the SVT is to perform the tracking of charged particles and the localization of the primary collision vertexes and of the secondary micro-vertexes, key to identifying weak decays. The Silicon Vertex Tracker (SVT) is the innermost subsystem of the future ePIC (electron-Proton-Ion Collider collaboration) detector [1,2]. It is designed to meet the performance required by the physics program at EIC (Electron-Ion Collider), the new accelerator facility that will be built at the Brookhaven National Laboratory (Upton, NY, USA) [3]. Top: detector schematic and pictorial view of IB and OB half-barrel. Bottom: required performances from the physics working group compared to a fast simulation of transverse momentum resolution and distance of closest approach of tracks. [1] Dalla Torre S., ”The ePIC detector at the EIC”, CERN Detector Seminar 2024, https://indico.cern.ch/event/1418391/ [2] Gonella L., "Development of a Silicon Vertex and Tracking Detector for the Electron-Ion Collider.”, The 32nd International Workshop on Vertex Detectors. [3] Khalek Abdul R. et al., "Science requirements and detector concepts for the electron-ion collider: EIC yellow report”, Nuclear Physics A 1026 (2022): 122447. [4] ALICE collaboration, "Technical Design report for the ALICE Inner Tracking System 3 - ITS3. A bent wafer-scale monolithic pixel detector", CERNLHCC-2024-003, https://cds.cern.ch/record/2890181 Inner Barrel The Inner Barrel (IB) is designed to provide precise vertex reconstruction with asymptotic resolution better than 10 µm, and contributing to momentum measurement. CAD exploded view of IB support with cables and sensors. Thermal FEA Simulation of the thermal load is ongoing for the quarter-barrel L0-L1 without the Left Endcap (power and data transfer, on wafer). Turbulence (critical for proper cooling) can not be easily achieved. Static temperature FEA VIN=15 m/s ΔT=~20℃ 32°C 46°C Air flow cooling and possible addition of other cooling elements are still under investigation. Measurements on mock-up with thermal load are needed to confirm the preliminary evaluation of cooling effectiveness. Heat exchange coefficient Overestimated in the simulation Material budget distribution as a function of pseudorapidity η, as obtained from simulation, is shown on the right. For η in range [-1,1] only sensors are present reaching 0.07%; elsewhere copper (likely to be replaced with aluminum) cables and services increase X/X0. CFC thickness is kept at the upper safe estimate value of 1 mm. Material budget last design Mechanical load simulations with a load safety factor of 1.5 are ongoing. L2 deformation results are extrapolated by L0-L1. Results from last support design simulations show an enhanced deformation on e-side arms. Mechanical FEA If support is made of separated parts glued together, the deformation is 600 µm on edges, due to copper cables, not affecting the sensor region. In this case CFC thickness of 200 µm is considered. IB is composed by three active layers: L0 - L1 - L2. The design foresees a cylindrical frame structure: each half-layer will consist of the sensors, a local carbon foam support structure and two sets of FPCs/ cables for powering and data/control transmission. IB will use the ALICE ITS3 [4] MAPS sensor MOSAIX fabricated in 65 nm commercial CMOS technology and thinned to 50 µm. MOSAIX has a pixel size of 21x23 µm2 and a power consumption of 40 mW/cm2. The sensors will be placed one next to the other and bent in a cylindrical shape radii of 37.5, 50 and 125 mm for L0, L1 and L2, respectively. IB structure glued separate parts design 200 µm CFC thickness! 2025 D. Colella (University and INFN Bari - [email protected]) R. Turrisi (INFN Padova - [email protected]) for the ePIC SVT detector subsystem collaboration The ePIC Silicon Vertex Tracker IB-OB: design and thermal-mechanical simulations