TF Coil Displacement Distortion FE Analysis Simulating Non-Constant Assembly Gap Between Wedging Interfaces of TF Coils

The early plasma ramp-up on ITER will be performed under a limiter configuration. In this early plasma phase, the possible misalignments between the plasma configuration and the ITER first wall panels (FWP) in the inboard regions can lead to an increase of the power flux density acting on the FWPs. This situation is considered as a safety risk for the machine: a significant increase of the flux density may exceed the design limits of the FWPs and damage the inboard modules. Therefore, in order to avoid an excessive increase of the power flux density on the FWPs, one of the main goals of the tokamak assembly strategy is to achieve the most symmetric magnetic field structure and the best blanket alignment. The symmetric toroidal field (TF) coils structure is key for achieving the symmetric magnetic field. In the ideal case, the assembly gap dimensions in the wedging interfaces of every two adjacent TF coils are designed as an uniform value, i.e., 2 mm. However, in reality the assembly gap tolerances can be generated during the manufacturing and assembly process of the TF coils, which can lead to the asymmetric TF coils structure configuration after energization. The purpose of this paper is to investigate and discuss the consequent displacement distortions of the TF coils by simulating the non-constant assembly gap distributions in a 360° mechanical FE model of the ITER TF system.