Mechanical challenges of the innermost layers of ePIC Silicon Vertex Tracker

At the Electron Ion Collider, the ePIC experiment intends to primarily investigate the origin ofthe nucleon mass and spin, nucleon tomography, the interaction of quarks and gluons in thenuclear medium, quark confinement and the properties of high-density gluon states. Thisbroad and variegated Physics plan requires novel and high-performing detectors. For example,the innermost barrel layers of the Silicon Vertex Tracker (SVT) consist of bent radiation-hardened MOSAIX chips, minimizing the material budget and multiple scattering effects in theregion close to the beam interaction point. The MOSAIX chips are being realised using TPSCo65 nm CMOS imaging technology and the stitching technique in flat 300 mm wafers. Themechanical bending occurs outside the company and during the assembly of the detectorlayers. Their design presents several mechanical and cooling challenges faced in synergy withthe ALICE-ITS3 project. However, the SVT layers will cover cylindric lateral surfaces with largerradii than ITS3 layers, which drives the need for dedicated R&D and solutions for large radii. Forexample, in SVT, the radius of the first layer is ~38 mm, whereas the ITS3 design foresees a ~19mm radius.The bending procedure and the local mechanical structure have been validated and optimisedon 50 μm-thick silicon dummies. The results of these studies will be presented.The successive steps consist of assembling of a multi-layer mock-up to finalise its constructiveprocedure, and a mechanical and thermal mock-up to perform the thermal and wind tunneltests. The last prototype will be equipped with temperature sensors and heaters, which mimicthe temperature distribution when the power is supplied. The measurements will validate thedesign of the final detector, and they will be compared with the ongoing simulations.In this contribution, the most recent design of the inner barrel SVT, bending, and bondingprocedures will be shown. A review of the bent Monolithic Active Pixel Sensor (MAPS) outcomeswill be also reported to give a more comprehensive picture of the state-of-the-art of thepresented technology.