Ricerc@Sapienza

One of the major technological challenges inherent to the tokamak, a toroidal chamber inside which a high temperature plasma is magnetically confined to produce fusion reactions, concerns the very large Lorentz forces (of the order of tens of MN) acting on the set of coils devoted to the generation of the toroidal component of the magnetic field (the Toroidal Field Coils, TFCs). If not properly counteracted with reinforcing structural material or other solutions, these forces can lead to the rupture of the coil.

Drastically reducing the force acting on the TFCs would lead to a simpler, more reliable, and more economical tokamak design. The Lorentz force is proportional to the intensity of the current running in the coil, the magnetic field produced by the coil, and the angle between the current and the magnetic field vectors: F = I x B x cos(I x B). It follows that the intensity of this force can be modified if the various regions of the coil (and thus the direction of the coil current running through it) are tilted in the toroidal direction by appropriate angles.

Supported by a Finanziamento d'Ateneo 2016, the P.I. of the present proposal has written a code which finds the force-minimizing angle along the entire perimeter of the TFC, and has conducted a series of initial studies on the tilted TFC concept [Reference 1: R. Gatto, F. Bombarda, "The differentially-tilted toroidal field coil concept for tokamaks", Fusion Engineering and Design, 147, 2019 (https://www.sciencedirect.com/science/article/pii/S0920379619307082?dgci...)].

Additional funds would make it possible the continuation of this line of research. In particular, next steps would include a more definitive design of the tilted TFC, a study of the equilibrium and stability properties of the plasma confined inside the tilted TFC system, the proposal of operational scenarios which take advantage of the vertical field due to the tilting, and a thermo-mechanical stress analysis of the tilted TFC.