For decades, physicists have been trying to understand and predict plasma behaviour in future reactor-scale tokamaks such as ITER and DEMO. Unfortunately, these hot, strongly magnetized plasmas are extremely complex and it was very quickly evident that the there was never going to be any other alternative than numerical simulations to describe the dynamics of plasma transport. Such simulations have thus always been an essential part of fusion research.
A simulation showing how the ''donut-shaped'' magnetic surfaces, which confine the plasma, break due to the onset of a disruption. The left figures show the intersections of magnetic field lines with a poloidal cross-section after several toroidal turns (see the arrows in the bottom-right figure for the toroidal and poloidal directions). Field lines that quickly intersect the walls are shown in blue, while red shows confined lines that do not leave the plasma or that leave it after hundreds of toroidal turns. On the right, iso-surfaces of plasma current density are shown together with the vacuum vessel currents (black arrows).