MICE experimental setup
The MICE experiment can be viewed as consisting of three different elements:
- A beamline to provide the required input muon beam
- A cooling channel to provide the required ionisation cooling
- A series of particle detectors to provide the required measurements of position and momentum, and particle identification
The cooling channel consists of three liquid hydrogen absorbers and two radio frequency (RF) cavities. The muons lose energy in the liquid hydrogen in all directions, the longitudinal component is then replaced in the RF sections. Liquid hydrogen was chosen as absorber because of its large ionisation energy loss rate (ie its cooling ability) and its low probability of multiple scattering (ie the heating it provides). Each hydrogen absorber is surrounded by a pair of focus coils. The RF system consists of eight 201 MHz cavities split into two four cavity sections.
In order to provide the necessary measuremenst both particle identification and tracking detectors are included. At the upstream end of the experiment two Time Of Flight (TOF) detectors and a Cherenkov allow us to identify whether the particle entering the channel is a muon. The particle then passes through two spectrometers, one before and one after the cooling channel, allowing its position and momentum to be measured before and after cooling and thus allowing measurements of cooling. Finally another TOF measurement along with a Cherenkov and calorimeter are situated at the downstream end to detect particles which decayed in flight.
In additional to the cooling channel and instrumentation, a carefully designed beam line is required to provide the required muon beam. The currently anticipated design is shown below:
A target is dipped into the beam halo just before extraction of the beam causing a spray of particles - mainly pions and protons. As many of these particles as possible are captured by a quadrupole triplet. The particles then pass through a dipole magnet which acts to analyse their momentum before they traverse a solenoid in which the pions decay to muons. The particles next pass through a second dipole selecting muons of the required momentum, before they finally encounter two more quadrupole triplets.