A
particle accelerator is a machine that uses
electromagnetic fields to propel
charged particles to very high speeds and energies, and to contain them in well-defined
beams.
[1]
Large accelerators are used for basic research in
particle physics. The largest accelerator currently operating is the
Large Hadron Collider (LHC) near Geneva, Switzerland, operated by the
CERN. It is a
collider accelerator, which can accelerate two beams of protons to an energy of 6.5
TeV and cause them to collide head-on, creating center-of-mass energies of 13 TeV. Other powerful accelerators are
KEKB at
KEK in Japan,
RHIC at
Brookhaven National Laboratory in New York and, formerly, the
Tevatron at
Fermilab, Batavia, Illinois. Accelerators are also used as
synchrotron light sources for the study of
condensed matter physics. Smaller particle accelerators are used in a wide variety of applications, including
particle therapy for
oncological purposes,
radioisotope production for medical diagnostics,
ion implanters for manufacture of semiconductors, and
accelerator mass spectrometers for measurements of rare isotopes such as
radiocarbon. There are currently more than 30,000 accelerators in operation around the world.
[2]
There are two basic classes of accelerators: electrostatic and electrodynamic (or electromagnetic) accelerators.
[3] Electrostatic accelerators use static
electric fields to accelerate particles. The most common types are the
Cockcroft–Walton generator and the
Van de Graaff generator. A small-scale example of this class is the
cathode ray tube in an ordinary old television set. The achievable
kinetic energy for particles in these devices is determined by the accelerating
voltage, which is limited by
electrical breakdown.
Electrodynamic or
electromagnetic accelerators, on the other hand, use changing electromagnetic fields (either
magnetic induction or oscillating
radio frequency fields) to accelerate particles. Since in these types the particles can pass through the same accelerating field multiple times, the output energy is not limited by the strength of the accelerating field. This class, which was first developed in the 1920s, is the basis for most modern large-scale accelerators.
Rolf Widerøe,
Gustav Ising,
Leó Szilárd,
Max Steenbeck, and
Ernest Lawrence are considered pioneers of this field, conceiving and building the first operational
linear particle accelerator,
[4] the
betatron, and the
cyclotron.
Because the target of the particle beams of early accelerators was usually the atoms of a piece of matter, with the goal being to create collisions with their nuclei in order to investigate nuclear structure, accelerators were commonly referred to as
atom smashers in the 20th century.
[5] The term persists despite the fact that many modern accelerators create collisions between two
subatomic particles, rather than a particle and an atomic nucleus.
[6][7][8]
