Part 5/10:
Fusion reactions release far more energy per unit of fuel than fission, the process that powers conventional nuclear reactors. However, the conditions required to sustain fusion are much more extreme. Whereas fission can be achieved at relatively low temperatures, fusion requires heating the fuel to tens of millions of degrees Celsius - hotter than the core of the Sun.
Maintaining these extreme conditions and containing the highly reactive plasma is the primary technical hurdle facing fusion researchers. Various reactor designs, such as the tokamak and stellarator, use powerful magnetic fields to confine and control the plasma. Other approaches, like inertial confinement fusion, use intense laser or particle beams to compress and heat the fuel.