The Neutrino Factory is a possible future accelerator facility that creates beams of neutrinos from the decays of muons in a storage ring. The neutrino beams from a Neutrino Factory would have the highest intensity and can be controlled with unprecedented accuracy. For these reasons, the Neutrino Factory has the potential to discover measurable differences between neutrino and antineutrino oscillations, which could be the key to understanding the puzzle of the matter-antimatter asymmetry of the universe. This phenomenon, known as CP violation, has been observed in the quark sector but has never been seen in the neutrino sector. A future Neutrino Factory would determine CP violation in the neutrino sector with the best possible accuracy. Furthermore, a Neutrino factory could be used as a first stage before the construction of a Muon Collider, which could be used to measure the properties of the Higgs boson with the ultimate precision, and could potentially reach energies of up to 6 TeV, in order to explore new physics phenomena at the highest energy frontier.
Both the Neutrino Factory and a Muon Collider rely on the acceleration of muons. To be able to create muon accelerator facilities, we require to reduce the size of the muon beam so that it may be accelerated. Since muons decay within 2 microseconds in their own rest frame, the only known way to reduce the phase space of the muon beam before the muons decay is to use the concept of ionisation cooling, in which the muons lose energy in an absorber such as liquid hydrogen or lithium hydride (LiH) and then recover the longitudinal component of the momentum by accelerating them using RF cavities. The international Muon Ionization Cooling Experiment (MICE) is an engineering demonstration of the concept of ionisation cooling. This experiment is being built at the Rutherford Appleton Laboratory, in which a beam of muons will be cooled in a muon cooling cell consisting of three absorbers and two RF cavities inside the field of two focus coil magnets.
The emittance of the beam is measured before and after the cooling channel using a scintillating fibre tracker inside a superconducting solenoid, and the muons are identified using time-of-flight detectors, a Cherenkov detector and a calorimeter system consisting of a scintillating fibre-lead pre-shower detector (named the KL) and a totally active scintillating detector, called the Electron Muon Ranger (EMR).
Image source: CERN