How are neutrons produced? Where can I get them? What methods have been used to produce free neutrons at neutron sources? Here you will explore the wide range of neutron sources from natural sources to transportable sources, high-flux and next generation sources.

Unlike photons, which are generated by numerous intense sources (light sources, heat sources, synchrotrons, etc), free neutrons sources are much more rare and infinitely weaker.
Industry, medicine and research use a wide range of transportable (movable) neutron sources. Neutrons are generated either by means of particles emitted by an artificial radioisotope, or by electronic generators that accelerate particles and bombard a target with them.
Additionally, isotopic sources are compact, but since in their case the ray emission cannot be stopped, security measures for transportation and usage are very restricting. This is why the industry has developed other neutron sources that can be stopped at any time. They are medium-power, continuous or pulsed sources that are compact enough to be portable or transportable.
The most intense neutron sources on Earth (except for atomic bombs) are production facilities, expensive and few in number. These use controlled fission of Uranium or Plutonium (nuclear reactors), or the bombarding of heavy nuclei with high-energy protons (spallation sources) to produce either a high continuous neutron flux or a high-brilliance pulsed neutron flux.

What are neutrons? How do neutrons interact with matter? Here some essential principles of physics are explained and the implications for the study of matter with neutrons.

Electrons, protons, neutrons are constituent particles of every atom; in turn, atoms are the constituents of our environment. Everybody has heard of electrons (the base of electronics) and protons (well known to chemists). The neutron is less popular or rather its image is more negative, doubtless because of atomic bombs. However, its role in research and industry is non negligible.

Neutrons play an important role in the study of the structure and dynamics of matter. Neutrons are often more penetrating than X-rays, they interact with atom nuclei rather than electron clouds, they directly "see" magnetic atoms. As a consequence, they provide both unique and complementary informations to X-ray techniques.
Discover how neutrons provide unique insights into scientific problems !

Besides sources, the use of neutrons requires the adequate know-how and technology. Scientists have developed a range of working methods that rely on the various neutron-matter interactions, as well as a series of technological devices for guiding, selecting, detecting neutrons and for placing the sample under research in the desired conditions.

Observing the organization of matter on a macroscopic scale or on the scale of a few atoms, studying internal movements on the scale of large atom groups or on an atomic level, all these require the use of adequate methods and tools. In time, researchers have developed suitable methods for each size and duration scale, by taking advantage of particular neutron properties and the ways they interact with matter.

The precise understanding of the neutron itself and of atom nuclei is essential for the progress of physics and astrophysics. In order to penetrate their secrets, numerous laboratories and scientists try to improve our knowledge of the particle neutron itself or to create very unusual nuclei called exotic nuclei. In other words, neutrons take part in this research on two accounts: as an object of study and as a tool for bombarding a target nuclei.

Guiding, controlling, focusing, dispersing neutron beams is essential for physics experiments. In the case of visible light, this is easy to accomplish via mirrors, lenses and prisms. In the case of neutrons, it is more difficult, but techniques have gradually been developed that give greater importance to either the corpuscular or wave nature of this particle.

Scientists investigate matter by using various types of rays and particles (photons, electrons, neutrons, muons, etc), because each of these can “see” different, complementary aspects of matter.

Neutrons are not used as much as they deserve, due to the relative weakness and scarcity of neutron sources. Despite this, neutrons are essential for the study of magnetism, movement inside matter, etc., and make a significant contribution to numerous other types of research.

Neutrons are very much involved in the study of atomic structure and the dynamics of soft matter (polymers, colloids, liquid crystals, gels, thin layers, etc). Neutrons are also similar to a small compass, able to test the magnetic moment of each atom inside a material. Thanks to this remarkable characteristic, they are essential for a number of magnetic material studies, which are of high scientific interest and economic importance.

On the other hand, certain problems are much easier to study with neutrons than with other techniques e.g. because they inflict less harm on fragile biological substances than other forms of radiation or because they are particularly good at “seeing” hydrogen atoms, which have a crucial role in biological processes. For all these reasons neutrons make certain types of observation possible that are difficult to conduct by any other method.
Other examples are the observation of the position of light atoms among a large number of heavy atoms, detailed observation of atomic and molecular motion in a range of energy of frequencies not or barely accesible to other techniques.

Thanks to their ability to easily penetrate important volumes of matter and to have a specific interaction with matter, neutrons are used for numerous kinds of applied research, difficult to realize without them: in medicine, metallurgy and materials, chemistry, soft matter, earth sciences and metrology.

Gamma rays, X-rays, ultraviolet radiation, infrared radiation, microwaves, positron, and electron radiation, etc.; have all led to major advances in medicine. Why not neutrons, then?

Due to the relative transparence of metals to neutrons, the in-situ evolution of chemical reactions inside complex devices can be followed, the remote detection of water presence, the detection of traces of poison and analysis, etc., all are possible thanks to neutrons.

Neutrons are involved in several fields of Earth Science. Their high penetrating power makes it possible to study rock texture in order to understand distortion mechanisms; their high sensitivity to hydrogen is used for measuring soil humidity, for oil or natural gas detection, for the study of ocean hydrates and for chemical reactions occurring at the surface of ice.

“Soft matter” (plastics, foams, gels, varnish, etc), which are so often encountered in our habitual environment, are not easy to understand and study. Again, neutrons are the ideal tool for these type of studies as well as for many others.

An essential task of metrology is the precise measurement of fundamental constants that govern physics and implicitly technology. Here are a few recent cases in which neutrons were involved in this type of research: gravitational constant, Avogadro number (N), neutron lifetime, neutron dipolar electrical moment, etc.

Civil production of electrical energy or space or military production of mechanical energy (propulsion) are amongst the many applications of neutrons.
Besides being used for the production of electricity in nuclear reactors, neutrons are used more and more in industry, medicine, agriculture, geology, etc. in very specialized but often essential applications.

What is the link between medical imaging, nuclear therapies and computer or electronic components in trains? The irradiation of materials via neutrons. Although poorly known to a general public, this is current practice in research, medicine and industry.
Moreover, while X-rays and other types of radiation are at the front of the medical stage, the role of neutrons in nuclear medicine is more discreet, yet very important.

What do continuous mineral analysis, explosives detection, and the detection of hidden drugs have in common? Neutrons, of course, that can traverse thick layers of material and selectively detect all types of atoms or isotopes.

Neutrons are also used for controlling compound materials made up of metal and organic products and thick materials. Measuring residual stress in solid materials, analyzing their texture, etc, are very important aspects of quality control and of improving the reliability of technological devices. Here again, using neutrons is an advantage.

The most intense neutron sources on Earth (except for atomic bombs) are industrial level facilities that use either controlled fission of Uranium or Plutonium (nuclear reactors) in order to generate a continuous or pulsed high neutron fluxes.

In 1950 the first reactor dedicated to scientific research was built. Its sole purpose was to create vast quantities of neutrons, which made it an extremely versatile scientific instrument. Research reactors are essentially nothing more than a source of neutrons.

Today, more than 30 laboratories in the world are equipped with neutron facilities, primarily used for research purposes.
During this virtual tour you will discover the world's largest research centers in neutron science, their activities and also their equipment available to the scientific and technical community.

Too often neutron scattering facilities appear as tools reserved for fundamental research, far from everyday practical applications.

Today nothing is further from the truth; Biology and pharmacy, micro-electronics, research on materials of highly diverse natures (metals, polymers, glass…), all necessitate close collaboration between public and private research. Neutron are increasingly involved in this process.