Beta radiation consists of high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei, a process known as beta decay. There are two primary forms: beta-minus (β-) and beta-plus (β+).
In beta-minus decay, a neutron in an unstable nucleus transforms into a Proton, emitting an electron (β-) and an antineutrino. This process increases the atomic number by one while the mass number remains unchanged. A classic example is the decay of Potassium-40 to Argon-40, or components of the Thorium Decay Chain like Radium-228 decaying to Actinium-228. This type of decay is prevalent in neutron-rich isotopes.
Beta-plus decay, or positron emission, occurs when a proton in an unstable nucleus transforms into a neutron, emitting a positron (β+) and a neutrino. This decreases the atomic number by one, with the mass number remaining constant. Positrons are antimatter equivalents of electrons; they quickly annihilate with electrons in the surrounding material, producing Gamma Radiation.
Beta particles are significantly lighter than Alpha radiation particles, but carry the same magnitude of charge. Their lower mass means they travel at much higher speeds and have a longer range in matter compared to alpha particles, but a shorter range than gamma rays. They interact with matter primarily through ionization and excitation of atomic electrons.
The penetrating power of beta radiation is moderate; it can be stopped by a few millimeters of aluminum or a few centimeters of plastic. Due to their charge, beta particles experience energy loss through collisions, a process characterized by Linear Energy Transfer.
Measuring beta radiation often involves instruments like Geiger counters. For personal monitoring, Personal Dosimeters are used. Exposure to beta radiation can cause skin burns (beta burns) and, if the source is ingested or inhaled, can contribute to internal dose. Many Naturally Occurring Radioactive Materials (NORM) contribute to beta exposure, especially isotopes within the Uranium Decay Series and Thorium Decay Chain. For instance, Uranium-238 undergoes alpha decay, but its decay products include many beta emitters. Similarly, Radium, specifically Radium-226, an alpha emitter, is often in Secular Equilibrium with beta-emitting daughters.
Comparing beta decay with other forms of radioactivity like Alpha radiation and Gamma Radiation is crucial for understanding nuclear safety principles. The concept of Half-Life is fundamental to understanding the decay rates of beta emitters.