Preliminary structural design of the IDEA Drift Chamber

The IDEA (Innovative Detector for Electron-positron Accelerator) drift chamber is a large, ultra-light gaseous tracking detector whose very low material budget is enabled by an innovative wire-support and assembly concept. Its large dimensions, combined with the requirements of low mass and high stiffness, pose significant challenges for structural design and material selection. This work presents a preliminary structural design of the wire cage, with particular emphasis on the endplates, which consist of an outer ring, an inner ring, radial spokes, and suspension cables supporting almost 340,000 anodic and cathodic wires. A hierarchical two-stage optimization strategy is adopted. In the first stage, Response Surface Methodology and Kriging surrogate models are used for geometric sizing, seeking a compromise between low structural mass, reduced spoke deformation, and adequate buckling resistance. In the second stage, a genetic algorithm is used to optimize the suspension-cable prestresses and further reduce spoke deflection. The optimized prestress distribution reduces the maximum spoke deflection from 24.34 mm to 0.564 mm. Although this value remains above the preliminary working target of 0.2 mm, the results demonstrate the effectiveness and structural feasibility of the cable-stayed endplate concept at the present preliminary-design stage. Further refinement will be required once the final composite material system and detector-level requirements have been defined.