Quantities for ionizing radiation
Fundamental Metrological Standards

Ionizing radiation is defined by the property of being able to strip electrons from matter, thereby producing ions. This definition encompasses a large number of charged particles (α, β, electrons, protons...) and uncharged particles (X or γ photons, neutrons). Their origin is also highly varied (gas pedals, X-ray generators, nuclear reactors, radioactive sources, cosmic rays).

The SI units referring to this radiation are derived units with special names (table 5): the becquerel (s^-1) for activity, the gray (J·kg^–1) for absorbed dose and the kerma (15th CGPM, 1975), and the sievert (J·kg^–1) for dose equivalents (16th CGPM, 1979)