A top-down modeling approach for DEMO magnetic system

The DEMO magnet system embodies a set of mechanical structures to join together the different Toroidal Field coils and to provide a suitable support to thermal, magnetic and gravitational loads. Over the years, different baselines have been produced which have required revisions and updates of the studies of the magnetic system and its supporting structures. This work presents a 3-level modeling approach which is fast and therefore suitable to evaluate different requirements. Following a top-down sequence, at the macro-level, a global 3D model of the entire tokamak is developed, which is very efficient (around 2 sec CPU time on a common laptop) and allows sensitivity studies and inverse design. At the intermediate level one sector of the system is considered, to evaluate the possible critical points. At the local level, detailed models of particular structures or parts of the system can be exploited, without compromising the computational efficiency. The consistency across the scale is guaranteed by imposing the conditions at the boundary taken from the preceding level.