Different types of radiation

Radioactive elements present in the environment emit alpha, beta and gamma radiation. However, other types of so-called ionizing radiation exist that are capable of causing atomic reactions.

 

Ionizing radiation includes:

(source from http://physique-eea.ujf-grenoble.fr/, picture originally produced by CERN) (source from http://physique-eea.ujf-grenoble.fr/, picture originally produced by CERN)

• Cosmic radiation, formed by particles that move at nearly the speed of light. They are made up of two components: (1) a continuous component of galactic origin and (2) a sporadic component of solar origin. The first component is caused by ions with very high energy levels coming from galaxies outside our solar system while the second component is essentially made up of protons. The interaction of cosmic radiation with the earth's magnetic field produced and maintains the magnetosphere that, together with the atmosphere, forms a protective barrier that lets only 0.05% of cosmic radiation reach sea level.

• Highly energetic electromagnetic waves such as X-rays and gamma rays. Thick walls of lead or concrete are required to stop X-rays and gamma rays.

 

X-rays can be generated by impacting an electron beam on a target. The electrons interact with the electrons of the target atoms, causing them to change energy levels and emit X-rays.

Gamma rays are emitted by radioactive atoms during their decay.

 

• Alpha, beta plus and beta minus corpuscular radiation. These types of radiation are formed by particles emitted by radioactive atoms during their decay.

(source from American Institute Physics) (source from American Institute Physics)

Alpha radiation is made up of a flux of helium nuclei, each nucleus being composed of two protons and two neutrons. It can be stopped by a sheet of paper.

 

Beta radiation (plus and minus) is made up of a flux of electrons and can be stopped by a thin sheet of aluminum or centimetric plate of wood.

(source from http://cnsc-ccsn.gc.ca/) (source from http://cnsc-ccsn.gc.ca/)

• Free neutrons present mainly in nuclear reactors. They are emitted for example during the fission of uranium-235 atoms. They are referred to as indirectly ionizing because they generate gamma rays and/or various particles when captured by or interacting with the nuclei. Neutron radiaton has a variable energy and light-weight materials containing in particular hydrogen are often required to stop it.