Nuclear fusion releases energy when light atomic nuclei combine into heavier nuclei; on Earth, fusion-energy research focuses on creating and controlling extremely hot plasma so useful reactions can occur repeatedly.
Fusion combines light nuclei
Atomic nuclei carry positive electric charge and repel one another. At sufficiently high temperature, particles move fast enough that some nuclei can approach closely enough for the strong nuclear force to bind them. If the final nucleus has slightly less mass than the starting nuclei, the mass difference appears as released energy.
The Sun uses fusion under enormous gravitational pressure. Earth-based reactors cannot copy the Sun’s pressure, so they rely on much higher temperatures and engineered confinement.
Why deuterium and tritium are common research fuels
Many fusion-energy programs focus on deuterium and tritium, two isotopes of hydrogen. Their reaction produces a helium nucleus and a high-energy neutron and has a comparatively large reaction probability at temperatures achievable in experimental plasmas.
Deuterium exists naturally in water. Tritium is radioactive and scarce, so future systems would need careful fuel handling and likely breed tritium from lithium-containing materials.
How fusion plasma is confined
Magnetic-confinement devices such as tokamaks use strong magnetic fields to keep charged plasma away from material walls. Inertial-confinement experiments use intense lasers or other drivers to compress tiny fuel targets for very short times.
Both approaches must reach a combination of temperature, density and confinement time sufficient for fusion reactions to become energetically significant.
Fusion energy is not yet commercial electricity
Experiments have achieved important milestones, including laboratory fusion ignition in inertial-confinement targets, but a power plant must also operate repeatedly, survive neutron exposure, manage heat, produce or supply fuel, maintain components and generate electricity economically.
Fusion research therefore combines plasma physics, nuclear engineering, materials science, superconducting magnets, lasers, robotics and power-system design.
