Speaker
Renato Gatto
(Department of Astronautical)
Description
Tokamak toroidal field coils (TFCs) characterized by a tilting in the azimuthal direction lead to several potential advantages, most notably the relieving of the stresses in the most critical area at the inboard side. As a consequence, much of the heavy steel structures needed to withstand the huge electromagnetic forces in conventional magnets can be reduced. Mechanically unloading the TFCs makes it easier to generate the fields required to approach ignition conditions at high density and relatively low temperature in compact devices.
An additional advantage of the tilted coil is that of generating poloidal field as well as toroidal field. If the former is used to provide at least some of the flux swing needed to induce the plasma current, then the discharge could be sustained for a longer time.
The “tilted coil” concept originates from an idea presented almost thirty years ago in two papers [1,2] dealing with the problem of generating large toroidal fields in compact tokamaks. In perspective, tilted coils could be made of ribbons of high temperature superconductors, characterized by high critical magnetic fields but rather poor structural properties.
The magnetic field produced by a system of tilted TFCs of different shapes (rectangular, circular, D-shaped) has been simulated with an ad hoc numerical code, and an optimization procedure was implemented to find the tilting angles that minimize the total force or its components in some direction. It is found that the radial force on the inner leg can be reduced by over a factor of ten, while in the remaining regions of the coil the forces are reduced by a lesser extent, and their direction change.
[1] A. Sestero, Comment. Plasma Phys. Controll. Fusion 11, 27 (1987).
[2] B. Coppi , L. Lanzavecchia,et al., Plasma Phys. Controll. Fusion 11, 47 (1987).
Co-authors
Francesca Bombarda
(FSN Fusion Physics Division, ENEA, Frascati (RM), Italy)
Renato Gatto
(Department of Astronautical, Electrical and Energy Engineering, Sapienza University, Rome, Italy)
