Effective Magnetic Field Computation in Tokamaks in Presence of Magnetic Materials

Magnetic materials play an important role in the magnetic fields distribution inside Tokamaks, and their contributions must be carefully computed. In some applications, when 3D geometries are involved and high accuracy must be achieved, finite elements may reveal too computationally demanding and different approaches must be considered. In this paper, two possible solutions are presented. The first one is based on the discretization of magnetic parts into rectangular prisms with constant magnetization density; analytical formulas are then used to compute the field contribution due to each brick. The second one is based on the representation of the effect of magnetic materials as a set of dipoles, by using again analytical formulas to evaluate the contribution to the magnetic field. Iterative procedures are applied to evaluate the magnetization density in prisms. The efficiency and accuracy of both models are validated against commercial codes on a test case, and then applied to the computation of magnetic field in presence of Neutral Beam Injector in an ITER-like geometry.