Beta particle

Beta particles are high-energy electrons or positrons emitted by certain types of radioactive nuclei such as potassium-40. The beta particles emitted are a form of ionizing radiation also known as beta rays. The production of beta particles is termed beta decay. They are designated by the Greek letter beta (β).

There are two forms of beta decay, β⁻ and β⁺, which respectively give rise to the electron and the positron.

β⁻ decay (electron)

Unstable atomic nuclei with an excess of neutrons may undergo β⁻ decay, where a neutron is converted into a proton, an electron and an electron-type antineutrino (the antiparticle of the neutrino):

$\mbox{n} \rightarrow \mbox{p} + \mbox{e}^- + \bar{\nu}_{e}$

A W minus Boson is emitted from the nucleus which then decays into an electron and an antineutrino. It does this by converting one of the two up quarks in the proton into a down quark, leaving two down quarks and one up quark (a Neutron) to convert an up quark into a down quark a -1 charge is carried away to observe charge conservation (the W- boson, then the electron, as an up quark carries a charge of +2/3 and the down quark has a charge of -1/3; this quark is said to have undergone a flavor change).

Uses

Beta particles can be used to treat health conditions such as eye and bone cancer, and are also used as tracers. The main element for these jobs is Strontium-90. Beta particles are also used in quality control to test the thickness of an item coming through a machine (paper coming through a roller being the most notable example). Some of the beta radiation is absorbed while passing through the product. Should the product get too thick then more radiation will be absorbed. A sensor will detect this and transfer more power to the rollers which will be pushed closer together to keep the material thin. Likewise if the material gets too thin the opposite will happen.

Technetium-99

Technetium-99 is also used as a tracer in medicine as a gamma-free source of beta particles. The half-life of Technetium-99 is relatively low, meaning that the damage to the body is limited.

References

http://www.epa.gov/radiation/radionuclides/strontium.htm

Radioactivity

Gourt Home::Gourt :: Beta particle

β− decay (electron)

Uses

Technetium-99

See also

References

β⁻ decay (electron)