The synchrotron evolved from the
cyclotron, the first cyclic particle accelerator. While a classical
cyclotron uses both a constant guiding
magnetic field and a constant-frequency
electromagnetic field (and is working in
classical approximation), its successor, the
isochronous cyclotron, works by local variations of the guiding magnetic field, adapting to the increasing
relativistic mass of particles during acceleration. In a synchrotron, the strength of magnetic field and RF frequency is varied during acceleration. and
Nicholas Christofilos allowed the complete separation of the accelerator into components with specialized functions along the particle path, shaping the path into a round-cornered polygon. Some important components are given by
radio frequency cavities for direct acceleration,
dipole magnets (
bending magnets) for deflection of particles (to close the path), and
quadrupole /
sextupole magnets for beam focusing. facility, a
synchrotron light source. Dominating the image is the
storage ring, showing a
beamline at front right. The storage ring's interior includes a synchrotron and a
linac. The combination of time-dependent guiding magnetic fields and the strong focusing principle enabled the design and operation of modern large-scale accelerator facilities like
colliders and
synchrotron light sources. The straight sections along the closed path in such facilities are not only required for radio frequency cavities, but also for
particle detectors (in colliders) and photon generation devices such as
wigglers and
undulators (in third generation synchrotron light sources). The maximum energy that a cyclic accelerator can impart is typically limited by the maximum strength of the magnetic fields and the minimum radius (maximum
curvature) of the particle path. Thus one method for increasing the energy limit is to use
superconducting magnets, these not being limited by
magnetic saturation.
Electron/
positron accelerators may also be limited by the emission of
synchrotron radiation, resulting in a partial loss of the particle beam's kinetic energy. The limiting beam energy is reached when the energy lost to the lateral acceleration required to maintain the beam path in a circle equals the energy added each cycle. More powerful accelerators are built by using large radius paths and by using more numerous and more powerful microwave cavities. Lighter particles (such as electrons) lose a larger fraction of their energy when deflected. Practically speaking, the energy of
electron/
positron accelerators is limited by this radiation loss, while this does not play a significant role in the dynamics of
proton or
ion accelerators. The energy of such accelerators is limited strictly by the strength of magnets and by the cost.
Injection procedure Unlike a cyclotron, synchrotrons are unable to accelerate particles from zero kinetic energy; one of the obvious reasons for this is that its closed particle path would be cut by a device that emits particles. Thus, schemes were developed to inject pre-accelerated
particle beams into a synchrotron. The pre-acceleration can be realized by a chain of other accelerator structures like a
linac, a
microtron or another synchrotron; all of these in turn need to be fed by a particle source comprising a simple high voltage power supply, typically a
Cockcroft–Walton generator. Starting from an appropriate initial value determined by the injection energy, the field strength of the
dipole magnets is then increased. If the high energy particles are emitted at the end of the acceleration procedure, e.g. to a target or to another accelerator, the field strength is again decreased to injection level, starting a new
injection cycle. Depending on the method of magnet control used, the time interval for one cycle can vary substantially between different installations. == History and development ==