The international Muon Ionisation Cooling Experiment

JB Lagrange, G Barber, D Colling, A Dobbs, P J Dornan, C Heidt, C Hunt, K Long, J Martyniak, S Middleton, J Pasternak, E Santos, M A Uchida, V Blackmore

Ionization Cooling is the only practical solution to preparing ultra-high intensity muon beams for a Neutrino Factory, the ultimate tool conceived for studying leptonic charge parity violation, or Muon Collider, a facility offering a route to multi-TeV lepton-anti-lepton collisions at the energy frontier.

Due to the short muon lifetime, traditional beam cooling techniques, used to shrink the beam phase space size (known as emittance), cannot be used. Ionization cooling is the process whereby a muon beam is passed through a material, called an absorber, where the muons lose both longitudinal and transverse momentum. The lost longitudinal momentum is restored using RF cavities following the absorber, leading to the desired reduction in emittance. As well as this cooling effect however, there is also a heating effect arising from multiple scattering, and the net cooling is a delicate balance between these two effects. The muon ionization cooling experiment (MICE) aims to demonstrated ionisation cooling for the first time, by producing a 10% reduction in muon beam emittance and to measure it with 0.1% accuracy.

MICE is under development at the Rutherford Appleton Laboratory (UK). The muon beamline has been commissioned, and the beams have been shown by direct measurement with the particle physics detectors to be adequate for cooling measurements, in rate, particle composition and emittance.

Measurements of the beam cooling properties of liquid-hydrogen, lithium hydride and other absorbers are planned for 2014-2016. A full cell of the ionization cooling channel, including RF re-acceleration, is under construction, see Figure 3 below. The design offers opportunities for tests with various absorbers and optics configurations. Results will be compared with detailed simulations of cooling channel performance for a full understanding of the cooling process. The MICE collaboration is international with contributions from continental Europe, Japan, the UK and the US.

Schematic of the International Muon Ionization Cooling Experiment (MICE), with the beam entering from the left.
Figure 1. Schematic of the International Muon Ionization Cooling Experiment (MICE), with the beam entering from the left.

The MICE group at Imperial College proposed, built and lead the implementation of the scintillating-fibre trackers that form the baseline instrumentation for the MICE spectrometers. The beam emittance will be measured using two such scintillating fibre trackers one on each side of the cooling channel, they will be mounted inside a 4T solenoid. As particles pass through the tracker, their position will be measured at 5 stations, each of which provides a position resolution of less than 0.5mm.  The completed tracker modules have been built and calibrated and are currently at RAL awaiting installation into the full MICE experiment.  A photograph of a completed tracker module can be seen in Figure 2.

Photograph of one of the completed scintillating-fibre trackers for MICE.
Figure 2. Photograph of one of the completed scintillating-fibre trackers for MICE.

Further information on MICE can be found by following one of the following links:

The MICE collaboration’s home page