By contrast, a stellarator  uses external magnetic fields to confine plasma in the shape of a donut, called a torus. These magnetic fields allow scientists to control the plasma particles and create the right conditions for fusion. Stellarators use external coils to generate a twisting magnetic field to control the plasma instead of inducing electric currents inside the plasma like a tokamak. There are several stellarators presently in the United States including Auburn University, Hampton University, Columbia University, and Princeton Plasma Physics Laboratory, the University of Illinois, and the University of Wisconsin. Examples of U.S. companies developing magnetic confinement systems are Commonwealth Fusion Systems, TAE Technologies, Tokamak Energy, Helion Energy, and Thea Energy.

In inertial confinement, high power lasers are used to rapidly compress a small capsule of fusion fuel to extreme temperatures and pressures. This approach is used, for example, in the National Ignition Facility at the U.S. Department of Energy (DOE) Lawrence Livermore National Laboratory. Examples of U.S. companies developing inertial confinement systems are Xcimer Energy, Focused Energy, ZAP Energy, and Shine Technologies.

Numerous potential fusion fuels are also being investigated. According to the U.S. Department of Energy, once developed, first-generation fusion plants will likely use a combination of  deuterium, lithium and Deuterium-tritium. Lithium is a critical resource for fusion because it is used to breed tritium.   The rare lithium-6 form of the metal (Li-6), which makes up of 7.5 per cent of all naturally occurring lithium is the most efficient for sustaining the fusion process. Li-6 is banned in the U.S. because of the mercury waste it generates. So most fusion power concepts rely on “enriched” lithium, where the Li-6 content has been boosted.