Nuclear Fusion: Bringing a star down to Earth

TL;DR

This paper reviews the principles of nuclear fusion on Earth, focusing on magnetic confinement in tokamaks, challenges like instabilities, and methods to mitigate them for sustainable energy production.

Contribution

It provides an overview of magnetic confinement techniques in tokamaks and discusses recent advances in controlling plasma instabilities such as ELMs.

Findings

Confinement in tokamaks can be optimized but may lead to instabilities.

Magnetic perturbations can reduce the impact of ELMs.

Understanding plasma physics is key to improving fusion stability.

Abstract

Nuclear fusion offers the potential for being a near limitless energy source by fusing together deuterium and tritium nuclei to form helium inside a plasma burning at 100 million kelvin. However, scientific and engineering challenges remain. This paper describes how such a plasma can be confined on Earth and discusses the similarities and differences with fusion in stars. It focusses on the magnetic confinement technique and, in particular, the method used in a tokamak. The confinement achieved in the equilibrium state is reviewed and it is shown how the confinement can be too good, leading to explosive instabilities at the plasma edge called Edge Localised modes (ELMs). It is shown how the impact of ELMs can be minimised by the application of magnetic perturbations and discusses the physics behind the penetration of these perturbations into what is ideally a perfect conducting plasma.