268
B. J. Holzer et al.
were done in the CERN SPS and compared with detailed simulations to obtain
reliable estimates of the heavy ion collimation efficiency in the LHC [95].
The LHC also collided Xe nuclei in 2017 [98] and may collide other species in
future, generally with a view to increasing the nucleon-nucleon luminosity.
In the collision of asymmetric species the 2-in-1 magnet design of the LHC
requires that the magnetic fields in two rings are the same (the two RHIC rings are
independent and can have different fields). For p–Pb operation it is then necessary to
have different revolution frequencies at injection and during the energy ramp [99].
Lead beams in the LHC at design energy have noticeable synchrotron radiation
damping times (6 h and 13 h longitudinally and transversally) that are of the
same order as the IBS emittance growth times (8 h and 13 h longitudinally and
transversally) [92].
6.10 Beam Cooling
F. Caspers · D. Möhl
6.10.1 Introduction
Beam cooling aims at reducing the size and the energy spread of a particle beam
circulating in a storage ring or in an ion trap. This reduction of size should not
be accompanied by beam loss; the goal is to increase the particle density [100].
Since the beam size varies with the focusing properties of the storage ring, it is
useful to introduce normalized measures of size and density. Such quantities are
the (horizontal, vertical and longitudinal) emittances and the phase-space density.
For our present purpose they may be regarded as the (squares of the) horizontal
and vertical beam diameters, the energy spread, and the density, normalized by the
focusing strength and the size of the ring to make them independent of the storage
ring properties. Phase-space density is then a general figure of merit of a particle
beam, and cooling improves this figure of merit. The terms beam temperature
and beam cooling have been taken over from the kinetic theory of gases. For
visualization one may imagine a beam of particles going around in a storage ring.
Particles will oscillate around the beam centre in much the same way that particles
of a hot gas bounce back and forth between the walls of a container. The larger
the mean square of the velocity of these oscillations in a beam, the larger the beam
size. The mean square velocity spread is used to define the beam temperature in
analogy to the temperature of the gas which is determined by the kinetic energy of
the molecules.
B. J. Holzer et al.
were done in the CERN SPS and compared with detailed simulations to obtain
reliable estimates of the heavy ion collimation efficiency in the LHC [95].
The LHC also collided Xe nuclei in 2017 [98] and may collide other species in
future, generally with a view to increasing the nucleon-nucleon luminosity.
In the collision of asymmetric species the 2-in-1 magnet design of the LHC
requires that the magnetic fields in two rings are the same (the two RHIC rings are
independent and can have different fields). For p–Pb operation it is then necessary to
have different revolution frequencies at injection and during the energy ramp [99].
Lead beams in the LHC at design energy have noticeable synchrotron radiation
damping times (6 h and 13 h longitudinally and transversally) that are of the
same order as the IBS emittance growth times (8 h and 13 h longitudinally and
transversally) [92].
6.10 Beam Cooling
F. Caspers · D. Möhl
6.10.1 Introduction
Beam cooling aims at reducing the size and the energy spread of a particle beam
circulating in a storage ring or in an ion trap. This reduction of size should not
be accompanied by beam loss; the goal is to increase the particle density [100].
Since the beam size varies with the focusing properties of the storage ring, it is
useful to introduce normalized measures of size and density. Such quantities are
the (horizontal, vertical and longitudinal) emittances and the phase-space density.
For our present purpose they may be regarded as the (squares of the) horizontal
and vertical beam diameters, the energy spread, and the density, normalized by the
focusing strength and the size of the ring to make them independent of the storage
ring properties. Phase-space density is then a general figure of merit of a particle
beam, and cooling improves this figure of merit. The terms beam temperature
and beam cooling have been taken over from the kinetic theory of gases. For
visualization one may imagine a beam of particles going around in a storage ring.
Particles will oscillate around the beam centre in much the same way that particles
of a hot gas bounce back and forth between the walls of a container. The larger
the mean square of the velocity of these oscillations in a beam, the larger the beam
size. The mean square velocity spread is used to define the beam temperature in
analogy to the temperature of the gas which is determined by the kinetic energy of
the molecules.