The neutron

The first part of the chapter introduces the relevant physical properties of the neutron and their relationship with kinetic properties. It explains neutron detection via the ionizing products of appropriate nuclear reactions. The second part deals with neutron sources. It explains the principle of research reactors (nuclear splitting) and the safety features (active, passive, inherent), and outlines the relationship between thermal flux, luminosity, and neutron current density. The low incident energy neutrons needed for QENS originate from so-called cold sources, mostly liquid deuterium. Alternatives to the research reactors are the neutron spallation sources, where high energy protons hit on nuclei of heavy elements and induce the ‘evaporation’ of neutrons. Pulsed spallation sources and continuous spallation sources are in operation nowadays, with certain advantages and disadvantages. From the cold source neutrons are led to the neutron scattering instruments in so-called neutron guides, where the principle of total reflection of the neutrons on the guide walls is utilized. Here, the use of super mirrors (multi-layer gradient coatings) has increased the available incident neutron intensity considerably.