What is a neutron?

May 23, 2012 at 12:05 pm 1 comment

Neutrons are all around you. You see them when you walk down the street. You can hear them right now. You taste them when you eat. You even felt them the moment you used your mouse. Is that air you are breathing right now ? or 50% neutrons?

~50% of You is made of neutrons.

(Actually these statements are not strictly true. You cannot experience neutrons directly. ESS could help you with that! They are, however, the building blocks of normal matter. )

The European Spallation Source ESS: A neutron facility for materials useful to science and society


A neutron is a subatomic particle; it is one of the building blocks of the atom. As such, it is found in the nucleus of an atom. The neutron has an atomic mass of about 1.00865 u, and a mass of about 1.675 x 10-27 kg. Its spin is +1/2 and that makes it a fermion. Additionally, it has no electric charge. A neutron is composed of two down quarks and an up quark, and these are bound together by the strong interaction (strong force).

A neutron is unstable when free in nature, and has a half life of about 886 seconds. The neutron could be said to be only “alive” to be part of an atomic nucleus as it ceases to exist after a while if left alone. When it wanders around loose, like after its release following a decay event or a fission event, it may bump into another atomic nucleus and become captured by it. This process is called – no surprise – neutron capture. It is, after all, a nucleon, as is a proton, both of which make up an atomic nucleus. When a neutron decays, a decay mediated by the weak interaction, it releases a proton (or, if you prefer, a hydrogen nucleus). Additionally, an electron, and an antineutrino are ejected. If you recognize this as beta minus decay, you are correct.

A neutron or neutrons can be practically released in one of two methods nuclear fission or the most efficient and safe method “spallation”. We build machines that take advantage of this phenomenon that perform fundamental research to help create and improve the materials our society will need in the future.

An example of an instrument that helps analyse materials with neutrons


A European large scale facility that will have a collection of instruments that help analyse materials using neutrons

The European Spallation Source



Entry filed under: General.

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1 Comment Add your own

  • 1. lista de emails  |  August 8, 2012 at 11:43 pm

    the post is really informative for me. i liked it very much. keep sharing such important posts. <a


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