1. (Muon Ionization Cooling Experiment)
the MICE experiment
(Muon Ionization Cooling Experiment)
A Neutrino Factory (NF) is a device conceived to produce a large amount of neutrinos (nm ,ne) in a very
clean way, due to the underlying physical process of their generation. These characteristics make the
NF a really powerful tool to investigate the ultimate properties of the leptonic sector (q13 mixing angle
and the measurement of a leptonic CP violation effect). To reach these goals we need to store ~ 1021
muons/yr.
A possible design for a NF foresees to store ~20 GeV muons in a “ring” where they decay along the
straight sections (m  nm + ne + e) generating the neutrinos suitable for the physics where the
phenomenon of neutrino oscillation is exploited to study the properties of neutrinos with great
precision. Since the mechanism of neutrino oscillation is used in the downstream detector the
optimal baseline is of the order of few 1000 km. A schematic view of the NF is shown in fig. 1
Muons are tertiary beams and are produced with a high emittance therefore they need to be cooled
before acceleration. The cooling must also be fast, given the short lifetime of the muon (t ~2 ms); this
fact puts conventional systems (e.g. stochastic cooling) out of the game. Ionization Cooling, instead,
appears to be the only practical technique. The principle (illustrated in fig.2) is quite simple: layers of
an absorber material and RF sections are alternated. The absorber causes an energy loss by
ionization of the charged particle crossing the medium, the RF cavity accelerates the muon in the
forward direction. The cooling effect is somewhat spoiled by the multiple scattering always present
when going trhough a material. At the proper initial emittance the overall effect is a reduction in the
transverse emittance.
The mechanism is “well known to work …”, theoretically. The goal of MICE is to prove the feasibility
of this principle by building a portion of a cooling channel and measuring its performances
MICE will be built at the Rutherford Laboratory (UK) in 6 steps, starting from a very basic
configuration to a final layout displayed in the cartoon of fig. 3 and on fig.4. It is an international
collaboration involving institutions from UK, Europe, United States, Japan and China.
Fig. 1: a possible layout of the Neutrino Factory
Fig. 2: principle of muon cooling and theoretical formula with the effects of cooling and multiple scattering
Fig. 3: emittance reduction in MICE
Optmizing the matching coil currents
emittance variation vs initial e
BZ along axis (T)
b (m)
Transmission of the channel
downstream
SPE (m rad)
 low Z absorber material
 tight focus (low b function)
 H2 is best absorber material
MICE steps
and phases
PHASE I
Emittance vs amplitude
PHASE II
Poster session, CERN accelerator school 2006, Zakopane