Everything about Beta Particle totally explained
Beta particles are high-energy, high-speed
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 emission)
An unstable atomic nucleus 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):
» → + +
This process is mediated by the
weak interaction. The neutron turns into a proton through the emission of a
virtual W− boson. At the
quark level, W
− emission turns a down-type quark into an up-type quark, turning a neutron (one up quark and two down quarks) into a proton (two up quarks and one down quark).
The virtual W
− boson then decays into an electron and an antineutrino.
Beta decay commonly occurs among the neutron-rich fission byproducts produced in nuclear reactors. Free neutrons also decay via this process. This is the source of the copious amount of electron antineutrinos produced by fission reactors.
β+ decay (positron emission)
Unstable atomic nuclei with an excess of
protons may undergo
β+ decay, also called inverse beta decay, where a proton is converted into a
neutron, a
positron and an electron-type
neutrino:
» → + +
Beta plus decay can only happen inside nuclei when the absolute value of the
binding energy of the daughter nucleus is higher than that of the mother nucleus.
Inverse beta decay is one of the steps in
nuclear fusion processes that produce energy inside stars.
Interaction with other matter
Being composed of charged particles, beta radiation is more strongly ionising than gamma radiation.
When passing through matter, a beta particle is decelerated by electromagnetic interactions and may give off
Bremsstrahlung.
Uses
Beta particles can be used to treat health conditions such as eye and bone cancer, and are also used as tracers.
Strontium-90 is the material most commonly used to produce beta particles. Beta particles are also used in quality control to test the thickness of an item, such as paper, coming through a system of rollers. Some of the beta radiation is absorbed while passing through the product. If the product is made too thick or thin, a correspondingly different amount of radiation will be absorbed. A computer program monitoring the quality of the manufactured paper will then move the rollers to change the thickness of the final product.
Inverse beta decay of a
radioactive tracer isotope is the source of the positrons used in
positron emission tomography (PET scan).
History
Henri Becquerel, while experimenting with
fluorescence, accidentally found out that
Uranium exposed a black paper wrapped
photographic plate with some unknown
radiation that couldn't be turned off like
X-rays.
Ernest Rutherford continued these experiments and discovered two different kinds of radiation:
- alpha particles that didn't show up on the Becquerel plates because they were easily absorbed by the black wrapping paper (actually just about any sheet of paper fully absorbs alpha particles)
- beta particles which are 100 times more penetrating that alpha particles.
He published his results in 1899.
Health
Beta particles are able to penetrate living matter to a certain extent (radiation intensity from a small source of radioactive material decreases as one over the distance squared) and can change the structure of struck molecules. In most cases such change can be considered as damage with results possibly as severe as cancer and death. If the struck molecule is
DNA it can show a spontaneous
mutation. If this mutated DNA is in
gametes the mutation may be passed to new generations. By far most mutations are considered genetic defects, it isn't proven if mutations caused by beta particle absorption could lead to positive
evolution.
Beta sources can be used in
radiation therapy to kill cancer cells.
Future use
Some sources claim that
betavoltaic cells will be available in the near future to supply power to laptops and mobile phones without ever recharging. These cells supposedly use
tritium as beta source.
Further Information
Get more info on 'Beta Particle'.
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