Neutron Scattering with Spallation Sources

The other articles in this issue are concerned with the variety of science that goes on at reactor‐based neutron sources. Such sources, based on nuclear fission, have been available since 1942. It has been known since the 1930s that neutrons could be produced through spallation by sending a charged beam of accelerated protons or electrons into a target. However, it has only been in the last few years that the intensity of these spallation sources has been sufficient for the range of sophisticated experiments required to study the properties of condensed matter. Today there are a number of operating spallation neutron sources, and more with higher intensity are planned (see the table). In this article we want to explain the difference between doing experiments at steady‐state and at pulsed sources, illustrate what has been done with the modest sources now available, and speculate on some future experimental efforts. We do not have space to describe how a spallation source works: this information is present...