Muons are used to study materials at the atom level. They are often used alongside neutrons to provide detailed information on atomic-level properties. ISIS is one of only four places in the world where it is possible to use muons for materials studies.
What is a muon? Well, muons aren’t part of the normal, everyday matter around us. They have to be specially made by collisions between other particles – in the case of ISIS, by collisions between the ISIS proton beam and a carbon target. They are an unusual tool to use to study materials, because they only live for two millionths of a second! But that is more than enough time to fire them into a material, for them to get an atom’s-eye view of what’s going on and for them to report this back to us.
Muons are particularly good at studying magnetic materials, where they are a very sensitive probe of magnetic ordering and dynamics. They are used to investigate the atomic-level workings of superconductors, materials which conduct electricity with no loss of energy. Muons can be used to study molecular motions and chemical reactions. They can be used as probes of hydrogen behaviour inside materials, and for studying how charges move inside conductors.
ISIS actually has two muon facilities – one funded by the UK and Europe, and one constructed by the Japanese RIKEN institute. Between them, they provide seven experimental areas for muon studies. See the ISIS web pages, and the ISIS muon group page, for more information. Muon beamtime at ISIS can be accessed in exactly the same way an neutron time – see the ISIS page on applying for beamtime.