Neutron sources: Neutrons are neutral particles found in the nuclei of every element excepting hydrogen. A beam of neutrons can be generated from special purpose research nuclear reactors for the study of how neutron interact with materials. Neutrons are not deflected by electrostatic interactions with nuclei but are sensitive to magnetic interactions. Due to the properties of their interactions they are widely used in studying new materials, magnetic materials as well as in the structure of how materials form at longer scales than can be easily addressed by diffraction sue to electromagnetic or x-ray radiation. Neutrons are electrically neutral but have a spin, or magnetic moment, so they they are sensitive to magnetic sources in condensed matter and can provide images of magnetic structure. Neutrons have the ability to deeply penetrate matter, they interact with nuclei and neutrons – unlike X-rays – can distinguish light elements such as hydrogen.
Muon sources: Muons are electrically charged elementary particles and can be thought of as short-lived heavy electrons. Particle physicists regard muons as heavy electrons – they have basically the same physical properties as electrons except for their mass being 207 times larger. There are both positively (µ+) and negatively (µ-) charged muons. Muons are unstable particles and decay with a half-life of a few millionths of a second. Since they only live such a short time, muons are not a component part of matter. And yet they are also found naturally in our world, as they are part of of cosmic background radiation and rain down on us all the time from high up in the earth’s atmosphere. Muon beams can be generated at similar but more specialised facilities then for neutrons, and these beams used for the study of materials. Muons when inserted into materials can take the place of an electron and the manner of their decay back to electrons can give unique information about the behaviour of electrons in the materials studied.
Further discussion of neutron beam research and muon beam research can be found at the NMI3 website. Currently four Irish research groups use neutron beam facilities and one Irish research group uses one of the European muon source facilities.
NMI3: “A description of NMI3’s activities”
NMI3: “What are muons and how are they produced at ISIS”
NMI3: “What are the advantages of working in a research project supported by NMI3″