Sievert Sievert The sievert (symbol: Sv) is a derived unit of ionizing radiation dose in the International System of Units (SI) and is a measure of the health effect of low levels of ionizing radiation on the human body. The sievert is of importance in dosimetry and radiation protection, and is named after Rolf Maximilian Sievert, a Swedish medical physicist renowned for work on radiation dose measurement and research into the biological effects of radiation. The sievert is used for radiation dose quantities such as equivalent dose and effective dose, which represent the risk of external radiation from sources outside the
Ionizing radiation nuclei, they are also sometimes written as or indicating a Helium ion with a +2 charge (missing its two electrons). If the ion gains electrons from its environment, the alpha particle can be written as a normal (electrically neutral) helium atom . Alpha particles are a hugely ionizing form of particle radiation. When they result from radioactive alpha decay they have low penetration depth. In this case they can be absorbed by a few centimeters of air, or by the skin. More powerful, long range alpha particles from ternary fission are three times as energetic, and penetrate proportionately farther in