Nuclear technologyparticles and energetic photons. Another desired effect is the detection of energetic particles.
Energy is released when the nucleus of a very heavy atom splits during fission. Energy is also liberated when two very light nucleii are made to combine into one heavier nucleus (fusion). In both cases this process cannot continue beyond the production of iron.
Fission occurs spontaneously in heavy nucleii but fusion requires extreme pressure and temperature. This is why fission reactorss are much easier to create than fusion reactors. Fission events liberate neutrons, which can induce an excited state in other nucleii, resulting in further fission events. By using the correct concentrations of materials and environment where at least one subsequent fission event will result from each initial fission event (on average), one creates a fission chain reaction. The energy released by this process is vastly greater than that resulting from any chemical reaction (including burning and explosion).
Energetic particles such as protons, neutrons, electrons and alpha particles (Hydrogen nucleii without any electrons) are detected in a variety of ways and for a variety of purposes. Radiac meters are used to determine the strength of radiation and to enhance safety. Some other more esoteric uses include determining a material's thickness or internal composition by measuring the level of radiation that passes through a target of known material.