30
An Introduction to Beam Physics
very high energies, colliders have a significant energy advantage over fixed
target machines because a very large fraction of the beams’ energies can be
converted to reaction energy. As a detailed study of the relativistic dynamics
shows, this is not at all the case for fixed target cases; in fact, conservation
of energy and momentum severely limits the energy that can be set free.
Large scaled circular colliders are those listed in Table 1.1, and the tunnel
with circumference 27 km, hosting the LHC currently, was earlier used for
the Large Electron-Positron Collider (LEP) (e
+ , e
− ; ∼ 100 GeV, 1989–2000).
Besides the energy advantage, storage rings also have the disadvantage of the
slow ramping times typical for synchrotrons; however, once the beam is stored,
it is essentially continuous again.
But also for situations that require the beam to hit a fixed target, storage
rings often offer an advantage over the use of synchrotrons by themselves,
because it is often possible to extract the beam much more slowly than in the
case of the synchrotron, resulting in a more easily manageable duty cycle and
reducing the problem of overflowing the electronics in the detectors. In this
method of ultra-slow extraction, the nonlinear dynamics of the device is
adjusted very carefully and gently, as over time a larger and larger part of the
originally stored emittance becomes unstable. If it is possible to control the
location around the ring where the spilling occurs, then the spilled particles
can be directed toward the fixed target as needed. One storage ring where
this approach is utilized is COSY, the cooler synchrotron and storage ring, at
Forschungszentrum J¨ ulich, Germany, shown in Fig. 1.21.
Another application of the storage ring that has become one of the most
productive tools for scientific research is the synchrotron light source.
Although not as majestic as the giant high energy colliders, there are many
synchrotron light sources throughout the world, and each facility hosts many
users from almost all disciplines of the sciences. In the light source, the probe
for the experiments is the light (from far infrared to hard X-ray) radiated
by the electrons when the orbits are bent in the ring, which is generated
through the process of synchrotron radiation. Figs. 1.22 [44] and 1.23
[42] show a couple of synchrotron light sources. As the electron mass is so
small, in principle, any bending magnet can be used to produce light due
to synchrotron radiation. But in addition, in the straight sections of a light
source ring, often wigglers and undulators, which consist of alternating
short bending magnets, are placed to produce more intense and coherent light.
In such a way, each light source ring can hold tens of light beamlines, much
more than the number of interacting locations that a high energy physics or
nuclear physics collider can have for the collider experiments.
An Introduction to Beam Physics
very high energies, colliders have a significant energy advantage over fixed
target machines because a very large fraction of the beams’ energies can be
converted to reaction energy. As a detailed study of the relativistic dynamics
shows, this is not at all the case for fixed target cases; in fact, conservation
of energy and momentum severely limits the energy that can be set free.
Large scaled circular colliders are those listed in Table 1.1, and the tunnel
with circumference 27 km, hosting the LHC currently, was earlier used for
the Large Electron-Positron Collider (LEP) (e
+ , e
− ; ∼ 100 GeV, 1989–2000).
Besides the energy advantage, storage rings also have the disadvantage of the
slow ramping times typical for synchrotrons; however, once the beam is stored,
it is essentially continuous again.
But also for situations that require the beam to hit a fixed target, storage
rings often offer an advantage over the use of synchrotrons by themselves,
because it is often possible to extract the beam much more slowly than in the
case of the synchrotron, resulting in a more easily manageable duty cycle and
reducing the problem of overflowing the electronics in the detectors. In this
method of ultra-slow extraction, the nonlinear dynamics of the device is
adjusted very carefully and gently, as over time a larger and larger part of the
originally stored emittance becomes unstable. If it is possible to control the
location around the ring where the spilling occurs, then the spilled particles
can be directed toward the fixed target as needed. One storage ring where
this approach is utilized is COSY, the cooler synchrotron and storage ring, at
Forschungszentrum J¨ ulich, Germany, shown in Fig. 1.21.
Another application of the storage ring that has become one of the most
productive tools for scientific research is the synchrotron light source.
Although not as majestic as the giant high energy colliders, there are many
synchrotron light sources throughout the world, and each facility hosts many
users from almost all disciplines of the sciences. In the light source, the probe
for the experiments is the light (from far infrared to hard X-ray) radiated
by the electrons when the orbits are bent in the ring, which is generated
through the process of synchrotron radiation. Figs. 1.22 [44] and 1.23
[42] show a couple of synchrotron light sources. As the electron mass is so
small, in principle, any bending magnet can be used to produce light due
to synchrotron radiation. But in addition, in the straight sections of a light
source ring, often wigglers and undulators, which consist of alternating
short bending magnets, are placed to produce more intense and coherent light.
In such a way, each light source ring can hold tens of light beamlines, much
more than the number of interacting locations that a high energy physics or
nuclear physics collider can have for the collider experiments.