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The Neutron Source
News and Events
User Office




Trends in Neutron Science - MLZ User Meeting 2015
February 23 - February 2413:00 - 14:00


Public awareness of research infrastructures
June 18 - June 1913:30 - 13:00


Moderators for optimal instrument performance at the ESS
January 12 14:30 - 15:30

The European Spallation Source will be the world’s leading neutron source for condensed-matter...
Polymer Composite Thermal Neutron Scintillator for Radiation Portal Monitors and Neutron Imaging
January 19 14:30 - 15:30

Thermal neutron detectors are used for medical imaging, nuclear plant safety, homeland, and border...
UCN optics for fundamental research at FRM II
January 26 14:30 - 15:30

Currently a powerful UCN source is under development and construction at the FRMII reactor in...
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What is a neutron?

animation neutronenzerfall neu
Free neutrons decay by emission of an electron and an electron antineutrino to become a proton after 14,8 minutes.

Neutrons are within nuclei of atoms. They belong to the group of the fundamental particles, the smallest known composites of the matter. They do not possess any electric charge, they are neutral. That is where the name neutrons comes from, which was invented by their discoverer James Chadwick (Discovery of the neutrons). The neutron's spin is ½, their mass 1,67 * 10-24 gramms. Free neutrons being outside of the nucleus can live for 886 seconds, almost 15 minutes - this is quite long for a fundamental particle. Then they decay by emission of an electron and an electron antineutrino to become a proton.

Free neutrons interact with fundamental particles within the nucleus, if they hit an atom. Thus, their effect on the atom depends on the number of neutrons and protons within the nucleus. Nuclei with a certain number of neutrons and protons are called nuclide. Nuclides with the same number of protons, but a different number of neutrons, are called isotopes (of an element). The interaction of X-rays with matter depends on the electrons of an atom and therefore all isotopes of an element interact the same way. But free neutrons interact with the particles within the nucleus causing different interactions for different isotopes of the same element (Why neutrons?).