3D Simulation of the Eddy-Current Losses in the Laminated, Ferromagnetic Nuclotron Yoke

The eddy-current losses are simulated using a 3D magnet model (Fig. 1). The magnetoquasistatic subset of the Maxwell equations is formulated in terms of line-integrated magnetic vector potential using the Finite Integration Technique for geometrical discretisation. The model is linearised by a successive-approximation technique with relaxation based on backtracking. A single-diagonal implicit Runge-Kutta method is used for time stepping. The ferromagnetic yoke is laminated along the axis of the magnet, here denoted by z. A non-conductive coating prevents currents to migrate between laminations. The individual laminations can not be resolved by the grid. Instead, an anisotropic conductivity tensor κ̄ = diag(κ, κ, 0) with κ the conductivity of iron, and an anisotropic reluctivity tensor ν̄ = diag(ν‖, ν‖, ν⊥) is used. The parallel and perpendicular reluctivities are computed from