6 Design and Principles of Synchrotrons and Circular Colliders
285
muons in the absorber and the length of the basic cell (Fig. 6.41) as:
1
ε i
dε i
ds
= J i
1
E μ
ΔE μ
Δs
.
(6.78)
A large number of cells or traversals through a cell is necessary to obtain
appreciable emittance reduction.
Almost by a miracle, the muon mass falls into a narrow ‘window’ where
ionisation cooling within the short life of the particle looks possible (although not
easy). For electrons as well as for protons and heavier particles, the method is not
practical, because the effect of bremsstrahlung (for e’s) and non-elastic processes in
the absorber (for p’s), leads to unacceptable loss.
With the revival of interest for muon colliders and, related to that, neutrino
factories [187], large collaborations (including more than 15 institutes, [188]) is
undertaking a demonstration experiment. The ISIS accelerator at the Rutherford
lab. is chosen for this task. Neutrino factory and muon collider proposals have to
rely critically on muon cooling: typically 50 m to several 100 m long channels with
solenoidal focussing (superconducting solenoids) are foreseen to reduce the phasespace of the muons emerging from pion decay. Liquid hydrogen absorbers, each
0.5–1 m in length, alternate with high-field accelerating cavities.
The variant selected by MICE is a ‘single particle experiment’ where one muon
at a time is traced. Fast spectrometers, capable of resolving 1 muon per 25 ns,
record/compare the three position coordinates and the three velocity components
of the muon at the entrance and the exit of a short cooling section. Typically such
a test-section should lead to 10% emittance reduction. The emittance pattern is
‘painted’ by a scatterer or a steering magnets changing the entrance conditions of
the particle at random (scatterer) or in a programmed manner. A large number of
muons are necessary to establish the six-dimensional phase-space reduction with
sufficient statistics.
Apart from the spectrometers, other challenges can be identified: long term
mechanical stability, muon decay and birth, contamination with other particles and
non-linarites in focussing which deform the emittance pattern. In the coming years
we will see a large effort on muon cooling scenarios and tests.
6.10.2.6 Cooling of Particles in Traps
In many experiments utilizing ion traps, the ions must first be cooled in order to
perform high precision measurements. Cooling refers here to the reduction of kinetic
energy of confined particles. A detailed review of cooling traps is given in [189] and
the implementation of several cooling methods into a big project is described in
[190].
With adequate modifications, most of methods discussed above for storage rings
stochastic- [191], electron- [192], or laser cooling [193] can also be applied to traps.
285
muons in the absorber and the length of the basic cell (Fig. 6.41) as:
1
ε i
dε i
ds
= J i
1
E μ
ΔE μ
Δs
.
(6.78)
A large number of cells or traversals through a cell is necessary to obtain
appreciable emittance reduction.
Almost by a miracle, the muon mass falls into a narrow ‘window’ where
ionisation cooling within the short life of the particle looks possible (although not
easy). For electrons as well as for protons and heavier particles, the method is not
practical, because the effect of bremsstrahlung (for e’s) and non-elastic processes in
the absorber (for p’s), leads to unacceptable loss.
With the revival of interest for muon colliders and, related to that, neutrino
factories [187], large collaborations (including more than 15 institutes, [188]) is
undertaking a demonstration experiment. The ISIS accelerator at the Rutherford
lab. is chosen for this task. Neutrino factory and muon collider proposals have to
rely critically on muon cooling: typically 50 m to several 100 m long channels with
solenoidal focussing (superconducting solenoids) are foreseen to reduce the phasespace of the muons emerging from pion decay. Liquid hydrogen absorbers, each
0.5–1 m in length, alternate with high-field accelerating cavities.
The variant selected by MICE is a ‘single particle experiment’ where one muon
at a time is traced. Fast spectrometers, capable of resolving 1 muon per 25 ns,
record/compare the three position coordinates and the three velocity components
of the muon at the entrance and the exit of a short cooling section. Typically such
a test-section should lead to 10% emittance reduction. The emittance pattern is
‘painted’ by a scatterer or a steering magnets changing the entrance conditions of
the particle at random (scatterer) or in a programmed manner. A large number of
muons are necessary to establish the six-dimensional phase-space reduction with
sufficient statistics.
Apart from the spectrometers, other challenges can be identified: long term
mechanical stability, muon decay and birth, contamination with other particles and
non-linarites in focussing which deform the emittance pattern. In the coming years
we will see a large effort on muon cooling scenarios and tests.
6.10.2.6 Cooling of Particles in Traps
In many experiments utilizing ion traps, the ions must first be cooled in order to
perform high precision measurements. Cooling refers here to the reduction of kinetic
energy of confined particles. A detailed review of cooling traps is given in [189] and
the implementation of several cooling methods into a big project is described in
[190].
With adequate modifications, most of methods discussed above for storage rings
stochastic- [191], electron- [192], or laser cooling [193] can also be applied to traps.