The neutron was discovered by Chadwick in 1932. It was soon realised that it was a very special, very useful particle that could provide unique and valuable insights into many aspects of materials. For example, the neutron is a magnet and is very sensitive to the magnetism inside materials. Correspondingly much of what we know and understand of magnetic materials has come from neutron scattering experiments. The neutron can also see light atoms, such as hydrogen and carbon, the very building blocks of life, better than any other radiation. Neutrons have therefore provided vital information on polymers, plastics and proteins, all of which are built from hydrogen.

The neutron’s ability to gently push and jostle atoms has enabled us to understand the complex processes of molecular motion and atomic vibrations, thereby improving our understanding of materials as diverse as glass, rubber and superconductors.

Cliff Shull and Bertram Brockhouse were two of the scientists who were quick to appreciate and exploit the special properties of the neutron. Half a century ago they pioneered many of the methods upon which our neutron “matterscopes” of today are based. It was Shull who demonstrated so clearly that the directions in which the neutrons are “elastically” scattered without changing speed provides information on the position and arrangement of atoms. Brockhouse showed that by measuring inelastic scattering, in which the neutrons change not just direction but also speed, the relative motion of the atoms, and therefore the forces holding the atoms together, could be studied. In recognition of these pioneering studies, and of the important role that their neutron scattering methods have now assumed in studies of materials of all kinds, Shull and Brockhouse received the 1994 Nobel Prize in Physics. Using neutrons they were able to show, in the words of the Nobel citation, “where atoms are and what atoms do”.

Read other interesting explanations:

In English with graphics: The Nobel Prize 1994

In English: What is a neutron?
(ISIS, UK)

Why use neutrons?
(ILL, FR)

Neutron - Wikipedia

Lecture notes: An Introduction to Neutron Scattering
Roger Pynn, Los Alamos National Laboratory, USA.

In German: Ein Spion für Physiker
(Uni Heidelberg - Germany)

In French: Neutrons:Particules révélateurs
(PNRM-Canada).

In Italian: Il neutrone Wikipedia

In Swedish: The ESS Scandinavia

Neutrone Wikipedia

See the picture of the Chadwick's toolbox "an old Rhodian cigarette carton in which he kept apparatus used in his scientific work" (Ingenious: the NMSI NOF-digitise project, UK)

Over the last fifty years more and more scientists from the fields of physics, chemistry, biology, materials, engineering, and geology have turned to neutrons to find the answers to the most complicated problems in their fields of research. In most cases neutrons have not just provided those answers but also more information besides. With neutrons we have “seen” deep inside the materials of our world and our new levels of understanding have led directly to novel materials, improvements of old materials, and better methods of materials processing.
But it is inevitable that, whether using the most powerful telescope or the most powerful microscope, the more one sees, the more one realises there is to see. We are now seeing the world at the very limits of our existing neutron matterscopes, but we know there is much more to be seen beyond the present horizon. Fortunately, we know exactly how we can arrange to see it.