Harnessing the energy of thermonuclear fusion reactions presents a promising solution to the growing demand for clean, safe, and sustainable energy. Under the extreme physical conditions required for energy production via fusion, matter exists in the plasma state. Plasma, often referred to as the fourth state of matter, is the most abundant form of visible matter in the universe as is found naturally in stars, including the Sun. In this state, any gas becomes ionized, consisting of free electrons and positive ions. Within the intense heat and pressure of stellar cores, light nuclei such as hydrogen can overcome their electrostatic repulsion and fuse together, releasing vast amounts of energy. This process, governed by Einstein’s mass-energy equivalencce equation, powers stars and holds great promise as a viable energy source on Earth due to its abundant fuel supply, minimal long-lived radioactive waste, and inherent safety. To replicate the necessary fusion conditions on Earth without the aid of a star’s immense gravitational confinement, we rely on the fact that plasma consists of charged particles allowing it to be confined using strong, carefully controlled magnetic fields in specialized reactors. Among the various reactor designs developed for this purpose, two have emerged as the most promising candidates for practical fusion energy: the tokamak and the stellarator.
The Tokamak
A tokamak is a device designed to harness the energy of fusion by confining hot plasma in a toroidal (doughnut-shaped) chamber using powerful magnetic fields. The goal is to replicate the conditions of stars by heating hydrogen isotopes to tens of millions of degrees, creating a plasma in which fusion reactions can occur. Magnetic fields, generated by coils surrounding the chamber and by currents within the plasma itself, keep the plasma stable and away from the reactor walls. Among various fusion reactor designs, the tokamak has emerged as one of the most advanced and studied due to its ability to sustain high-temperature plasmas and produce promising experimental results.