The International Muon Ionization Cooling Experiment (or MICE) is a
high energy physics
Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) and b ...
experiment
An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into Causality, cause-and-effect by demonstrating what outcome oc ...
at the
Rutherford Appleton Laboratory
The Rutherford Appleton Laboratory (RAL) is one of the national scientific research laboratories in the UK operated by the Science and Technology Facilities Council (STFC). It began as the Rutherford High Energy Laboratory, merged with the Atlas ...
. The experiment is a recognized
CERN
The European Organization for Nuclear Research, known as CERN (; ; ), is an intergovernmental organization that operates the largest particle physics laboratory in the world. Established in 1954, it is based in a northwestern suburb of Gene ...
experiment (RE11).
MICE is designed to demonstrate
ionization cooling In accelerator physics, ionization cooling is a physical process for reducing the beam emittance of a charged particle beam ("cooling") by passing the particles through some material, reducing their momentum as they ionize atomic electrons in the ma ...
of
muon
A muon ( ; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 '' e'' and a spin of , but with a much greater mass. It is classified as a lepton. As wi ...
s.
This is a process whereby the
emittance of a beam is reduced in order to reduce the beam size, so that more muons can be accelerated in smaller aperture accelerators and with fewer focussing magnets. This might enable the construction of high intensity muon accelerators, for example for use as a
Neutrino Factory The Neutrino Factory is a proposed particle accelerator complex intended to measure in detail the properties of neutrinos, which are extremely weakly interacting fundamental particles that can travel in straight lines through normal matter for thous ...
or
Muon Collider
A Muon Collider is a proposed particle accelerator facility in its conceptual design stage that collides muon beams for precision studies of the Standard Model and for direct searches of new physics. Muons belong to the second generation of lept ...
.
MICE will reduce the transverse emittance of a muon beam over a single 7 m cooling cell and measure that reduction. The original MICE design was based on a scheme outlined in Feasibility Study II., it was revised significantly in 2014.
Pions will be produced from a target in the
ISIS neutron source
The ISIS Neutron and Muon Source is a pulsed neutron and muon source, established 1984 at the Rutherford Appleton Laboratory of the Science and Technology Facilities Council, on the Harwell Science and Innovation Campus in Oxfordshire, Unite ...
and transported along a beamline where most will decay to muons before entering MICE. Cooling is tested with
lithium hydride
Lithium hydride is an inorganic compound with the formula Li H. This alkali metal hydride is a colorless solid, although commercial samples are grey. Characteristic of a salt-like (ionic) hydride, it has a high melting point, and it is not solub ...
(LiH) crystals or
liquid hydrogen
Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form.
To exist as a liquid, H2 must be cooled below its critical point of 33 K. However, for it to be in a fully li ...
(LH
2) cells, magnets are used to focus and analyze the muon beam. MICE will measure cooling performance over a range of beam momenta between about 150 and 250 MeV/c.
Beamline
The MICE muon beamline provides a low intensity muon beam for MICE.
Pions
In particle physics, a pion (or a pi meson, denoted with the Greek letter pi: ) is any of three subatomic particles: , , and . Each pion consists of a quark and an antiquark and is therefore a meson. Pions are the lightest mesons and, more gene ...
will be transported from a target dipping into the fringe of the ISIS proton beam, through a pion decay channel, into a muon transport line and then into MICE. For efficient use of muons it is desirable to have a reasonably good match between the transport beamline and the cooling channel, with selection performed in analysis. Also, the beamline must suppress non-muon events from entering the cooling channel. A beam rate of a few hundred muons per second is expected.
Experiment setup
MICE combines systems to identify, track, steer and cool muons.
To reject background from pions and electrons,
Cerenkov detector
A Cherenkov detector (pronunciation: /tʃɛrɛnˈkɔv/; Russian: Черенко́в) is a particle detector using the speed threshold for light production, the speed-dependent light output or the speed-dependent light direction of Cherenkov radi ...
s and
time of flight
Time of flight (ToF) is the measurement of the time taken by an object, particle or wave (be it acoustic, electromagnetic, etc.) to travel a distance through a medium. This information can then be used to measure velocity or path length, or as a w ...
detectors are the outermost components of the experiment. A calorimeter at the end distinguishes electrons from muons.
The muon emittance is measured with scintillating-fibre tracking detectors in a 4 Tesla magnetic field both before and after the main cooling cell. A diffuser can be placed in front of the first tracking detector to study cooling of muon beams with larger emittance.
The main cooling cell consists of a secondary LiH absorber, a
radio frequency cavity (RF cavity), coils to focus the beam onto the central main absorber (LiH or LH
2), magnet coils to focus the beam leaving the main absorber, a second RF cavity and another secondary LiH absorber.
While the secondary absorbers contribute to cooling, their main purpose is to stop electrons released in the RF cavities. The RF cavities are designed to accelerate the muons. As they cannot be synchronized with the incoming muons, some muons will be accelerated while others will be decelerated. The time of flight measurements allow a calculation of the electric field the muons experienced in the cavities.
The baseline main absorber is a LiH disk 65 mm thick. Alternatively, a 350 mm long liquid hydrogen vessel can be used.
Detectors
Muons pass through the cooling channel one by one. The muons' phase space coordinates will be measured by time of flight scintillators and scintillating fibre tracking detectors upstream and downstream of the cooling channel. Muons will be distinguished from other particles in the beam using a combination of the spectrometers and the so-called Particle Identification (PID) detectors, three time of flight scintillators, a Cerenkov detector and a calorimeter.
Status
As of 2017, MICE is taking data, and upgrades to a longer cooling cell are considered.
[Presentation by Kenneth Richard Long at th]
47th Muon Ionization Cooling Experiment (MICE) Collaboration Meetingpdf
References
External links
Official websiteMICE experiment record
experiment on INSPIRE-HEP INSPIRE-HEP is an open access digital library for the field of high energy physics (HEP). It is the successor of the Stanford Physics Information Retrieval System (SPIRES) database, the main literature database for high energy physics since the 1970 ...
{{coord missing, Oxfordshire
Particle experiments
Particle accelerators
CERN experiments
Research institutes in Oxfordshire
Science and Technology Facilities Council
Vale of White Horse