Mechanical pre-dimensioning and pre-optimization of the tokamaks' toroidal coils featuring the winding pack layout

The structural integrity of superconducting magnets that are key elements of a fusion reactor must be ensured. At an early design stage relatively simple calculation tools can greatly facilitate design optimization. The main objective of this paper is the mechanical pre-dimensioning of the tokamak toroidal field coils by simple means prior to the global 3D numerical modeling. A semi-analytical calculation tool that reasonably estimates the static strength of the toroidal field coil under the electromagnetic forces at the critical location (inner leg equatorial plane) is described. The novelty of the approach is that it treats not only the massive coil casing but also the winding pack conductor jacket under an essentially 3D stress state. The calculation tool features pre-optimization of the coil winding for graded layered winding layouts. The minimum space (radial built) required for the coil inboard portion that is a key design parameter is defined after possible winding pre-optimization. The procedure has been successfully benchmarked against numerical solutions and has been used for pre-dimensioning the toroidal coils in the frame of the current 2015 DEMO activity.