Multiscale Stress Analysis and 3D Fitting Structure of Superconducting Coils for the Helical Fusion Reactor

Conceptual design studies for the Large-Helical-Device-type helical reactor, i.e., FFHR-d1, are being conducted in the National Institute for Fusion Science. Three different cooling schemes and conductor types have been proposed for the superconducting magnet system. A multiscale structural analysis is used to assess the mechanical characteristics of the magnet structure, taking into account the types of cooling schemes and superconductors. Multiscale analysis evaluates both the stress distribution in the coil support structure and local stress in the constituents of the superconductors without rebuilding a finite-element model of the support structure. Concerning a segmented fabrication of the helical coils using a high-temperature superconductor, the feasibility of segment installation is confirmed using a three-dimensional printing model, which identifies the maximum segment length and the necessary gap in the coil casing to install a segment.