International Muon Ionization Cooling Experiment - Cooling Channel

Cooling Channel

The final MICE magnetic lattice is made up of 18 superconducting coils. Three solenoid coils provide a constant field for each of the two MICE tracking detectors and matching coils match the beam from the spectrometers into, and out of, the cooling channel. Each of the three absorbers sits between two focus coils. These focus the muon beam in the absorbers to provide optimal cooling. At the centre of each RFCC module, a single coupling coil creates the second harmonic term in the field that improves the range of momenta that the cooling channel can accept.

The MICE linacs consist of four normal-conducting copper cavities approximately 430 mm in length and 610 mm in radius. The RF cavities operate at 201.25 MHz with a peak field of 8 MV/m. The full muon energy will be replaced for muons that pass through the rf cavities on-crest. As there is no time distribution in the incoming beam, muons at all phases will be sampled.

The cavities must have a large aperture in order to avoid significant scraping from the high emittance beam. Hence, 0.38 mm thick beryllium windows are used to electromagnetically seal the cavities to avoid a high shunt impedance. These are nearly invisible to the muon beam. The windows have been designed to prevent electromagnetic heating from buckling the windows.

The baseline MICE absorber consists of a 21-litre, 350 mm long liquid hydrogen vessel sealed with a pair of curved, cylindrically symmetric aluminium windows at each end and cooled using cryocoolers. The absorber is removable, so that different materials may be used. For example, solid absorbers constructed from materials such as lithium hydride may replace the liquid hydrogen absorbers.