Effect of a TBM on the Toroidal Magnetic Field Ripple in the ITER and Measures to Reduce the Ripple

The ITER (International Thermonuclear Experimental Reactor) tokamak has 18 toroidal magnetic field (TF) coils, and the discreteness of these TF coils causes toroidally non-axisymmetric perturbations of the magnetic field. It is called a TF ripple and could lead to losses of high-energy particles, and an unfavorable heat load on the plasma facing components. In the ITER design, a ferromagnetic insert (FI) is employed to reduce the TF ripple, and an optimization of the FI design is ongoing. Also, since test blanket modules (TBMs) will be installed in the ITER, which are made of a ferromagnetic material, they also affect the TF ripple. We assessed the effects of the thickness of the FIs on the TF ripple in order to optimize the FI. And we analyzed how the TBMs distort the TF, and calculated the TF ripple for various amounts of a ferromagnetic material and the positions of the TBMs. A simple correction coil was adopted in order to reduce the TBM induced TF ripple to the required value of 0.3 %. We proposed technically available measures to reduce the TF ripple to the required value