Beta particles are radiation emitted by the radioactive decay of a heavy nucleus and this process is called beta decay. As the result of beta decay, two types of beta particles are emitted which are high-speed and high-energy electrons or positions. Electrons (e−) are emitted as a result of β− decay (electron emission) while positrons (anti-electron particle e+) are formed during β+ decay (positron emission) which are very rare.
In 1899, Ernest Rutherford published his work on Henri Becquerel’s experiment and discovered alpha radiation and beta radiation. In 1900, Henry Becquerel again worked on his experiment and measured the charge-to-mass ratio (e/m) for beta particles by using the method of J.J Thomson which is used for the identification of electrons.
After the experiment of Henry Becquerel, he suggested that beta particles are electrons due to the same (e/m) ratio for beta particles and Thomson’s electrons.
Properties of beta (β) particles
These are the following properties of beta (β) rays:
The deflection of beta particles in an electric or magnetic field shows that they are negatively charged particles. Their e/m ratio is the same as that of electrons indicating that beta particles are fast-moving electrons.
The velocity of beta particles is almost equal to the light and the average value is 2 x 108 ms-1.
Beta particles have a small mass and that is why they have low ionization power than alpha particles and more ionization power than gamma particles.
Beta rays have low kinetic energy and have very little effect on the zinc sulfide plate, whereas the photographic activity of beta particles is greater than alpha particles.
The high speed of beta particles gives more penetrating power than alpha particles. They have 100 times more penetrating power than alpha particles. Beta particles can be stopped by the 3 mm of aluminum or lead plate. This is due to their small mass and they are easily deflected from the path by an electric or magnetic field.
Common sources of beta (β) Particles
These are the most important sources of beta particles:
Beta (β) decay
Beta decay is the best source for the formation of beta particles. These are the two types of beta decay:
β− decay is the emission of electrons (beta particles). During the process, an unstable heavy nucleus with neutrons undergo beta decay in which the neutron is converted into three components: a proton, an electron, and an electron anti-neutron.
neutron → p + e− + ν−e
There is a weak interaction between the components during the process. By the emission of the W− boson, the neutron is converted into a proton. During the process, at the quark level boson emission convert the down quark into an up quark and turn a neutron (one up quark and two down quark) into a proton (two up quark and one down quark). Then finally, the W− boson decays into an electron and electron anti-neutrino.
β+ decay is the emission of positrons (beta particles). In this decay, unstable nuclei with an excess of positrons undergo beta-positron decay called positron decay or emission. During the process, a proton is converted into three components: a neutron, a positron, and an electron neutrino.
proton → n + e+ + νe
This type of beta decay only occurs inside nuclei, when the absolute value of binding energy of the new-forming nucleus (daughter) is greater than the parent nucleus. This means daughter nuclei have a lower energy state.
Fission products are used as the sources for the production of beta particles which are:
Strontium-90 is an alternative source of beta particles. It is used in industries as a beta emitter. Its derivatives also act as beta emitters, for example, when strontium-90 decays, it gives yttrium-90 which is also a beta emitter.
Strontium-89 has a short life for the production of beta particles. It is also used for the treatment of bone tumors.
Neutron activation products
Neutron activation products have the ability to use as beta particle emitters. These are the best beta particle emitters:
Tritium has low energy and is used as a beta particle emitter. It is also used as a radiotracer in the field of research. Beta particles emit from the tritium have average decay energy of 5.7 KeV and they are not detected by the Geiger counter.
Carbon-14 is the best source of beta particle production. These beta particles have also low energy but more than the beta particles that are emitted by tritium. This type of beta particle source is used in the field of research as a radiotracer in organic compounds.
Phosphorous-32 is a short-lived beta particle source and is used as a radiotracer. Beta particles produced by the emission of phosphorous-32 have more energy than tritium and carbon-14. They are also called high-energy beta emitters and have a half-life of 14 days.
Nickel-63 can be used as a source of beta particles and has a half-life of 100.1 years. It is also used as an energy source in Radioisotope Piezoelectric Generators.
Interaction of beta (β) particles with matter
Beta particles interact with matter and penetrate it a few millimeters. For example, when beta particles strike the aluminum plate, some of the beta particles are stopped and some of them penetrate deep into the plate. This is because when beta particles decelerate in the matter, they emit secondary gamma rays which have a more penetrating power as compared to beta particles.
Beta particles are charged particles and have strong ionizing power than gamma rays. When passed through the lead or aluminum plate, their speed reduces due to electromagnetic interaction with matter.
Beta radiation emits from the nuclear fission products and moves with the speed of light or exceeds. This radiation produces blue Cherenkov radiation when interacting with a water medium.
Detection and measurement of beta (β) particles
Beta particles can be detected and measured by the ionizing or excitation property. Radiometric detection instruments or tools are used to detect and measure beta radiation.
These are instruments that are used in the detection of beta particles:
- Geiger-Muller counter
- Ion chambers
- Scintillation counters
These are radiation quantities with SI unit:
- Activity (A) is the quantity and becquerel (Bq) is the SI unit.
- Exposure (X) is the quantity and coulomb per kilogram (C/kg) is the SI unit.
- Adsorbed dose (D) has a SI unit of gray (Gy).
- Equivalent dose (H) and effective dose (E) have the SI unit of sievert (Sv).
Absorbed dose (D) is the amount of radiation in the irradiated material. This is equal to the numerical value of the equivalent dose (E) with an SI unit of sievert (Sv) instead of gray (Gy). They have the stochastic biological effect of radiation on human tissues.
Applications of beta (β) particles
These are the following applications of beta particles:
Beta particles are used in the field of health treatment. They are used as tracers to treat eye and bone cancer. In such cases, strontium-90 is used as the source of beta particles.
Beta radiation or rays are also used to check the quality of products. For example, they are used to test the thickness of papers that directly comes out from the roller machine. During the process of passing the beta particles through the product, some beta particles are absorbed and the product is identified as a standard sample.
When the product is too thin or thick, it absorbed different amounts of beta particles which is different from the amount of radiation absorbed by the standard sample. In this way, products with different thicknesses are returned to the roller and recycled them.
Beta particles are used in illuminating devices. For example, betalight is an illumination device that contains tritium as a source and a phosphor. When tritium decay, it emits beta particles which strike the phosphor. As result, phosphor produces light or photons. There is no external power used with such devices and light depends on the decay of the tritium. The amount of light or illumination reduces to half in 12.32 years which is the half-life of tritium.
Beta particles are used in the positron emission tomography (PET) scan. In such cases, radioactive tracer isotopes are used as the source of beta particles.
What are the health effects of exposure to beta particles?
Beta particles have a harmful effect on the skin because they can penetrate through it and cause skin burns. As compared to alpha particles, beta particles have less ionization power but still, they are most dangerous when inhaled or digested.
What are some common sources of beta particles?
These are some common sources of beta particles:
What are some uses of beta particles?
Beta particles can be used for different purposes, such as
- They can be used in illuminating devices.
- Beta particles are used in the treatment of eye or bone cancer.
- They can use to check the quality of products such as the thickness of the paper.
What is the difference between an electron and a beta particle?
Electrons have a negative charge whereas beta particles have two types, one is the electron with a negative charge and the other is the positron with a positive charge.
Secondly, we can say that electrons and beta particles are the same due to the same mass-to-charge ratio. This is because positrons are emitted in the rare causes.
Is a beta particle antimatter?
The positron is the beta particle anti-matter or anti-electron particle.
What charge do beta particles have?
The beta particle has the same charge-to-mass ratio as electron and they have a negative charge because they deflect toward the positive plate under a magnetic or electric field.
Why does aluminum stop beta particles?
When beta particles strike the aluminum plate, some of the beta particles are stopped and some of the beta particles (secondary gamma particles) are moved through it. But the majority of beta particles are stopped by the aluminum plate due to low penetrating power as compared to gamma rays.