Turbulent plasma tamed by mathematics
A team from EPFL is successfully reviewing existing models describing plasma, this very high temperature ion-and-electron soup. Tested using simulations, this revision paves the way for a better understanding of the design of nuclear fusion reactors, such as ITER.
A very high temperature matter – over 10,000°C – plasma is commonly known as the fourth state of matter, as it differs from the other three: solid, liquid and gas. Paolo Ricci’s group is studying the models that describe this mixture of atomic nuclei and free electrons. This topic is relevant to the majority of the universe of stars and galaxies, which are themselves made of plasma.
On Earth, it is difficult to manipulate plasma because of its high temperature. Sensitive to magnetic and electric fields, it can thus be confined within a fusion reactor. It is also necessary to isolate it in a vacuum, to avoid any contact with surrounding matter. However, since it is a fluid, plasma is turbulent, and this can lead to it touching the inner wall of the confinement chamber.
A rewarding approach
Scientists have studied the interactions that take place when plasma enters in contact with matter. Their research avenue – focused on basic theoretical plasma physics – is not widespread in Europe, where the experimental approach is preferred. Their initiative has been successful.
A member of this group, doctoral student Joaquim Loizu has started from scratch, and more rigorously, to model the contact with the plasma. Some important approximations have thus been brought to light. However, they are not valid under all conditions, especially during interactions at the periphery of the plasma. Validated using simulations, which required very high computional power, this work will be verified experimentally by Ambrogio Fasoli and Ivo Furno’s group, thanks to TORPEX, within a year or so.
“Fusion is a promising field, in particular with the ITER project, in which Switzerland is also involved”, explains Paolo Ricci. This project is trying to develop a nuclear fusion reactor and master the energy which makes the stars shine. He also adds: “In order to be used industrially, this technique will inevitably have to master with more precision the interactions between the plasma and the confinement chamber.”
In astrophysics, the electromagnetic zone surrounding our planet, which is called the Van Allen belt, is also made of plasma, which orbiting satellites pass through. This progress will enable improvements in the design of these satellites, and even a reduction of detrimental effects on telecommunications.