Alfasäte

Alfasäte, or alpha radiation, refers to the emission of alpha particles during radioactive decay. An alpha particle consists of two protons and two neutrons, that is, the nucleus of a helium atom, and carries a +2 elementary charge. Alpha decay occurs primarily in very heavy nuclei as the nucleus seeks a more stable configuration.

The emitted alpha particle typically has kinetic energy in the range of about 4 to 8 MeV, which gives it a high ionization density along its short path. In matter, alpha particles interact strongly with electrons, causing ionization and excitation but not deep penetration. Their practical range is only a few centimeters in air, and they are stopped by a sheet of paper or even the outer layer of the skin. External exposure from a sealed source or clean surface is generally low, but the main health risk arises if alpha-emitting materials are ingested or inhaled, since particles deposited in tissues can cause significant local damage.

Common alpha-emitting isotopes include uranium-238, uranium-235, thorium-232, radium-226, plutonium-239, and americium-241. Owing to their properties, alpha sources are used in smoke detectors (notably americium-241), calibration of radiation detectors, and certain laboratory research applications. Handling and use are governed by radiation protection standards and licensing to prevent ingestion, contamination, and environmental release.

Detection and measurement rely on devices such as scintillation counters, gas-filled detectors, and solid-state detectors, with activity commonly expressed in becquerels and dose or risk considerations in sieverts depending on context. Alfasäte thus represent a highly ionizing but weakly penetrating form of radiation, demanding careful containment and proper safety practices.