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"Atom Smasher" redirects here. For other uses, see Atom Smasher (disambiguation).
A 1960s single stage 2 MeV linear Van de Graaff accelerator, here opened for maintenance
A 1960s single stage 2 MeV linear Van de Graaff accelerator, here opened for maintenance

A particle accelerator (or atom smasher[1]) is a device that uses electric fields to propel electrically-charged particles to high speeds and to contain them. In Physics, the space surrounding an Electric charge or in the presence of a time-varying Magnetic field has a property called an electric field (that can Electric charge is a fundamental conserved property of some Subatomic particles which determines their Electromagnetic interaction. In Particle physics, an elementary particle or fundamental particle is a particle not known to have substructure that is it is not known to be made An ordinary CRT television set is a simple form of accelerator. The cathode ray tube (CRT is a Vacuum tube containing an Electron gun (a source of electrons and a Fluorescent screen with internal or There are two basic types: linear accelerators and circular accelerators.

This page describes types of particle accelerators. For a list of existing and historic particle accelerators see: List of accelerators in particle physics. A list of Particle accelerators used for Particle physics experiments

Contents

Uses of particle accelerators

Beams of high-energy particles are useful for both fundamental and applied research in the sciences. For the most basic inquiries into the dynamics and structure of matter, space, and time, physicists seek the simplest kinds of interactions at the highest possible energies. These typically entail particle energies of many GeV or more, and the interactions of the simplest kinds of particles: leptons (e. Leptons are a family of fundamental Subatomic particles comprising the Electron, the Muon, and the Tauon (or tau particle as well as their g. electrons and positrons) and quarks for the matter, or photons and gluons for the field quanta. The positrons or antielectron is the Antiparticle or the Antimatter counterpart of the Electron. In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena Gluons ( Glue and the suffix -on) are Elementary particles that cause Quarks to interact and are indirectly responsible for the In quantum field theory (QFT the forces between particles are mediated by other particles Since isolated quarks are experimentally unavailable due to color confinement, the simplest available experiments involve the interactions of, first, leptons with each other, and second, of leptons with nucleons, which are composed of quarks and gluons. Color confinement, often called just confinement, is the Physics phenomenon that Color charged particles (such as Quarks cannot be isolated singularly In Physics a nucleon is a collective name for two Baryons the Neutron and the Proton. To study the collisions of quarks with each other, we resort to collisions of nucleons, which at high energy may be usefully considered as essentially 2-body interactions of the quarks and gluons of which they are composed. In Particle physics, the parton model was proposed by Richard Feynman in 1969 as a way to analyze high-energy Hadron collisions Thus elementary particle physicists tend to use machines creating beams of electrons, positrons, protons, and anti-protons, interacting with each other or with the simplest nuclei (eg, hydrogen or deuterium) at the highest possible energies, generally hundreds of GeV or more. The antiproton ( pronounced p-bar) is the Antiparticle of the Proton. Deuterium, also called heavy hydrogen, is a Stable isotope of Hydrogen with a Natural abundance in the Oceans of Earth

At a higher level of complexity, nuclear physicists and cosmologists may use beams of bare atomic nuclei, stripped of electrons, to investigate the structure, interactions, and properties of the nuclei themselves, and of condensed matter at extremely high temperatures and densities, such as might have occurred in the first moments of the Big Bang. Nuclear physics is the field of Physics that studies the building blocks and interactions of Atomic nuclei. Physical cosmology, as a branch of Astronomy, is the study of the large-scale structure of the Universe and is concerned with fundamental questions about its The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom Condensed matter physics is the field of Physics that deals with the macroscopic physical properties of Matter. The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation. These investigations often involve collisions of heavy nuclei--of atoms like iron or gold--at energies of several GeV per nucleon. In Physics a nucleon is a collective name for two Baryons the Neutron and the Proton. At lower energies, beams of accelerated nuclei are also used in medicine, as for the treatment of cancer.

Besides being of fundamental interest, high energy electrons may be coaxed into emitting extremely bright and coherent beams of high energy photons--ultraviolet and X ray--via synchrotron radiation, which photons have numerous uses in the study of atomic structure, chemistry, condensed matter physics, biology, and technology. This article concerns the physical phenomenon of synchrotron radiation Examples include the ESRF in Europe, which has recently been used to extract detailed three - dimensional images of insects trapped in amber [2] Thus there is a great demand for electron accelerators of moderate (GeV) energy and high intensity. ESRF redirects here for the medical condition see End stage renal failure The European Synchrotron Radiation Facility is a joint research facility

High-energy machines

Beam lines leading from the Van de Graaf accelerator to various experiments, in the basement of the Jussieu Campus in Paris
Beam lines leading from the Van de Graaf accelerator to various experiments, in the basement of the Jussieu Campus in Paris

Linear high-energy accelerators use a linear array of plates (or drift tubes) to which an alternating high-energy field is applied. The Jussieu Campus ( Campus Universitaire de Jussieu) is a higher education Campus located in the 5th arrondissement of Paris, France Paris (ˈpærɨs in English; in French) is the Capital of France and the country's largest city As the particles approach a plate they are accelerated towards it by an opposite polarity charge applied to the plate. As they pass through a hole in the plate, the polarity is switched so that the plate now repels them and they are now accelerated by it towards the next plate. Normally a stream of "bunches" of particles are accelerated, so a carefully controlled AC voltage is applied to each plate to continuously repeat this process for each bunch.

In early particle accelerators a Cockcroft-Walton voltage multiplier was responsible for voltage multiplying. This piece of the accelerator helped in the development of the atomic bomb. Built in 1937 by Philips of Eindhoven it currently resides in the National Science Museum in London, England.
In early particle accelerators a Cockcroft-Walton voltage multiplier was responsible for voltage multiplying. The Cockcroft-Walton (CW generator, or multiplier, was named after the two men who in 1932 used this circuit design to power their Particle accelerator, performing This piece of the accelerator helped in the development of the atomic bomb. A nuclear weapon is an explosive device that derives its destructive force from Nuclear reactions either fission or a combination of fission and fusion. Built in 1937 by Philips of Eindhoven it currently resides in the National Science Museum in London, England. Koninklijke Philips Electronics NV ( Royal Philips Electronics Inc. Eindhoven ( is a Municipality and a city located in the province of Noord-Brabant in the south of the Netherlands, originally at the confluence For science museums in general check out Science museum. The Science Museum on Exhibition Road, South Kensington, London is part London ( ˈlʌndən is the capital and largest urban area in the United Kingdom. England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland

As the particles approach the speed of light the switching rate of the electric fields becomes so high that they operate at microwave frequencies, and so RF cavity resonators are used in higher energy machines instead of simple plates. A resonator is a device or system that exhibits Resonance or resonant behavior that is it naturally oscillates at some frequencies, called its resonance

DC accelerator types capable of accelerating particles to speeds sufficient to cause nuclear reactions are Cockcroft-Walton generators or voltage multipliers, which convert AC to high voltage DC, or Van de Graaff generators that use static electricity carried by belts. The Cockcroft-Walton (CW generator, or multiplier, was named after the two men who in 1932 used this circuit design to power their Particle accelerator, performing A voltage multiplier is an Electrical circuit that converts AC electrical power from a lower Voltage to a higher DC voltage by means of Capacitors and A Van de Graaff generator is an electrostatic machine which uses a moving belt to accumulate very high electrostatically stable Voltages on a hollow metal globe

The largest and most powerful particle accelerators, such as the RHIC, the LHC (scheduled to start operation in 2008) and the Tevatron, are used for experimental particle physics. The Relativistic Heavy Ion Collider (RHIC pronounced like " Rick " ˈrɪk is a heavy- Ion Collider located at and operated by Brookhaven Tevatron is a circular Particle accelerator at the Fermi National Accelerator Laboratory in Batavia Illinois and is the highest energy particle collider In scientific inquiry an experiment ( Latin: Ex- periri, "to try out" is a method of investigating particular types of research questions or Particle physics is a branch of Physics that studies the elementary constituents of Matter and Radiation, and the interactions between them Particle accelerators can also produce proton beams, which can produce "proton-heavy" medical or research isotopes as opposed to the "neutron-heavy" ones made in fission reactors. Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides An example of this type of machine is LANSCE at Los Alamos. Los Alamos National Laboratory (LANL (previously known at various times as Site Y, Los Alamos Laboratory, and Los Alamos Scientific Laboratory) is a

Low-energy machines

Everyday examples of particle accelerators are those found in television sets and X-ray generators. X-radiation (composed of X-rays) is a form of Electromagnetic radiation. Low-energy accelerators such as cathode ray tubes and X-ray generators use a single pair of electrodes with a DC voltage of a few thousand volts between them. The cathode ray tube (CRT is a Vacuum tube containing an Electron gun (a source of electrons and a Fluorescent screen with internal or X-radiation (composed of X-rays) is a form of Electromagnetic radiation. An electrode is an Electrical conductor used to make contact with a nonmetallic part of a circuit (e Direct current ( DC) is the unidirectional flow of Electric charge. In an X-ray generator, the target itself is one of the electrodes. A low-energy particle accelerator called an ion implanter is used in the manufacture of integrated circuits. Ion implantation is a Materials engineering process by which ions of a material can be implanted into another solid thereby changing the physical properties of the Microchipsjpg|right|thumb|200px|Microchips ( EPROM memory with a transparent window showing the integrated circuit inside

Linear particle accelerators

Main article: Linear particle accelerator

In a linear accelerator (linac), particles are accelerated in a straight line with a target of interest at one end. Linacs are very widely used - every cathode ray tube contains one. The cathode ray tube (CRT is a Vacuum tube containing an Electron gun (a source of electrons and a Fluorescent screen with internal or They are also used to provide an initial low-energy kick to particles before they are injected into circular accelerators. The longest linac in the world is the Stanford Linear Accelerator, SLAC, which is 3 km (2 miles) long. The Stanford Linear Accelerator Center ( SLAC) is a United States Department of Energy National Laboratory operated by Stanford University under SLAC is an electron-positron collider. The positrons or antielectron is the Antiparticle or the Antimatter counterpart of the Electron.

The now disused Koffler particle accelerator at the Weitzmann Institute, one of Israel's most accomplished institutions of higher learning in the sciences.
The now disused Koffler particle accelerator at the Weitzmann Institute, one of Israel's most accomplished institutions of higher learning in the sciences. The Weizmann Institute of Science (מכון ויצמן למדע known as Machon Weizmann is a university and research institute in Rehovot, Israel.

Linear accelerators are also widely used in medicine, for radiotherapy and radiosurgery. Radiation therapy (or radiotherapy) is the medical use of Ionizing radiation as part of Cancer treatment to control Malignant Radiosurgery, also known as stereotactic radiotherapy is a Medical procedure which allows non-invasive treatment of benign and malignant conditions avascular malformations Medical grade LINACs accelerate electrons using a klystron and a complex bending magnet arrangement which produces a beam of 6-30 million electron-volt (MeV) energy. A klystron is a specialized linear-beam Vacuum tube (evacuated electron tube The electrons can be used directly or they can be collided with a target to produce a beam of X-rays. X-radiation (composed of X-rays) is a form of Electromagnetic radiation. The reliability, flexibility and accuracy of the radiation beam produced has largely supplanted the older use of Cobalt-60 therapy as a treatment tool. Cobalt-60 (60Co is a Radioactive isotope of Cobalt, with a Half life of 5

Tandem electrostatic accelerators

In a tandem accelerator, the negatively charged ion gains energy by attraction to the very high positive voltage at the geometric centre of the pressure vessel. When it arrives at the centre region known as the high voltage terminal, some electrons are stripped from the ion. The ion then becomes positive and accelerated away by the high positive voltage. Thus, this type of accelerator is called a 'tandem' accelerator. The accelerator has two stages of acceleration, first pulling and then pushing the charged particles. An example of a tandem accelerator is ANTARES (Australian National Tandem Accelerator for Applied Research). The Australian National Tandem Accelerator for Applied Research, ANTARES, is a Particle accelerator operated by ANSTO at the research establishment at

Circular or cyclic accelerators

In the circular accelerator, particles move in a circle until they reach sufficient energy. The particle track is typically bent into a circle using electromagnets. An electromagnet is a type of Magnet in which the Magnetic field is produced by the flow of an electric current. The advantage of circular accelerators over linear accelerators (linacs) is that the ring topology allows continuous acceleration, as the particle can transit indefinitely. Another advantage is that a circular accelerator is relatively smaller than a linear accelerator of comparable power (i. e. a linac would have to be extremely long to have the equivalent power of a circular accelerator).

Depending on the energy and the particle being accelerated, circular accelerators suffer a disadvantage in that the particles emit synchrotron radiation. This article concerns the physical phenomenon of synchrotron radiation When any charged particle is accelerated, it emits electromagnetic radiation and secondary emissions. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. Secondary emission is a phenomenon where additional electrons called Secondary electrons, are emitted from the surface of a material when an incident particle (often charged As a particle traveling in a circle is always accelerating towards the center of the circle, it continuously radiates towards the tangent of the circle. This radiation is called synchrotron light and depends highly on the mass of the accelerating particle. This article is mostly concerned with applications of Synchrotron radiation. For this reason, many high energy electron accelerators are linacs. Certain accelerators (synchrotrons) are however built specially for producing synchrotron light (X-rays). A synchrotron is a particular type of cyclic Particle accelerator in which the magnetic field (to turn the particles so they circulate and the electric field (to accelerate X-radiation (composed of X-rays) is a form of Electromagnetic radiation.

Since the special theory of relativity requires that matter always travels slower than the speed of light in a vacuum, in high-energy accelerators, as the energy increases the particle speed approaches the speed of light as a limit, never quite attained. Special relativity (SR (also known as the special theory of relativity or STR) is the Physical theory of Measurement in Inertial This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner. Therefore particle physicists do not generally think in terms of speed, but rather in terms of a particle's energy or momentum, usually measured in electron volts (eV). In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product An important principle for circular accelerators, and particle beams in general, is that the curvature of the particle trajectory is proportional to the particle charge and to the magnetic field, but inversely proportional to the (typically relativistic) momentum. A particle beam is an accelerated stream of Charged particles or Neutrons (often moving at very near the Speed of light) which may be directed by Magnets In Mathematics, curvature refers to any of a number of loosely related concepts in different areas of geometry Special relativity (SR (also known as the special theory of relativity or STR) is the Physical theory of Measurement in Inertial In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product

Cyclotrons

The earliest circular accelerators were cyclotrons, invented in 1929 by Ernest O. Lawrence at the University of California, Berkeley. A cyclotron is a type of Particle accelerator. Cyclotrons accelerate Charged particles using a high- Frequency, alternating Voltage (potential Ernest Orlando Lawrence ( August 8, 1901 – August 27, 1958) was an American physicist and Nobel Laureate best known for his The University of California Berkeley (also referred to as Cal, Berkeley and UC Berkeley) is a major research university located in Berkeley Cyclotrons have a single pair of hollow 'D'-shaped plates to accelerate the particles and a single large dipole magnet to bend their path into a circular orbit. A dipole magnet, in Particle accelerators is a Magnet constructed to create an homogeneous Magnetic field over some distance It is a characteristic property of charged particles in a uniform and constant magnetic field B that they orbit with a constant period, at a frequency called the cyclotron frequency, so long as their speed is small compared to the speed of light c. A cyclotron is a type of Particle accelerator. Cyclotrons accelerate Charged particles using a high- Frequency, alternating Voltage (potential This means that the accelerating D's of a cyclotron can be driven at a constant frequency by a radio frequency (RF) accelerating power source, as the beam spirals outwards continuously. The particles are injected in the centre of the magnet and are extracted at the outer edge at their maximum energy.

Cyclotrons reach an energy limit because of relativistic effects whereby the particles effectively become more massive, so that their cyclotron frequency drops out of synch with the accelerating RF. The term Mass in Special relativity usually refers to the Rest mass of the object which is the Newtonian mass as measured by an observer moving along with Therefore simple cyclotrons can accelerate protons only to an energy of around 15 million electron volts (15 MeV, corresponding to a speed of roughly 10% of c), because the protons get out of phase with the driving electric field. If accelerated further, the beam would continue to spiral outward to a larger radius but the particles would no longer gain enough speed to complete the larger circle in step with the accelerating RF. Cyclotrons are nevertheless still useful for lower energy applications.

Synchrocyclotrons and isochronous cyclotrons

Main article: Synchrocyclotron

There are ways of modifying the classic cyclotron to increase the energy limit. A synchrocyclotron is a Cyclotron in which the frequency of the driving RF electric field is varied to compensate for the mass gain of the accelerated particles as their velocity This may be done in a continuous beam, constant frequency, machine by shaping the magnet poles so to increase magnetic field with radius. Then higher energy particles travel a shorter distance in each orbit than they otherwise would, and can remain in phase with the accelerating field. Such machines are called isochronous cyclotrons. Their advantage is that they can deliver continuous beams of higher average intensity, which is useful for some applications. The main disadvantages are the size and cost of the large magnet needed, and the difficulty in achieving the higher field required at the outer edge.

Another possibility, the synchrocyclotron, accelerates the particles in bunches, in a constant B field, but reduces the RF accelerating field's frequency so as to keep the particles in step as they spiral outward. This approach suffers from low average beam intensity due to the bunching, and again from the need for a huge magnet of large radius and constant field over the larger orbit demanded by high energy.

A magnet in the synchrocyclotron at the Orsay proton therapy center
A magnet in the synchrocyclotron at the Orsay proton therapy center

Betatrons

Main article: Betatron

Another type of circular accelerator, invented in 1940 for accelerating electrons, is the Betatron. Orsay is a commune of Essonne, Île-de-France located in the southwestern suburbs of Paris, France. Proton therapy is a type of Particle therapy which utilizes a beam of Protons to irradiate diseased tissue most often in the treatment of cancer A betatron is a Cyclotron developed by Donald Kerst at the University of Illinois in 1940 to accelerate electrons The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J A betatron is a Cyclotron developed by Donald Kerst at the University of Illinois in 1940 to accelerate electrons These machines, like synchrotrons, use a donut-shaped ring magnet (see below) with a cyclically increasing B field, but accelerate the particles by induction from the increasing magnetic field, as if they were the secondary winding in a transformer, due to the changing magnetic flux through the orbit. Achieving constant orbital radius while supplying the proper accelerating electric field requires that the magnetic flux linking the orbit be somewhat independent of the magnetic field on the orbit, bending the particles into a constant radius curve. These machines have in practice been limited by the large radiative losses suffered by the electrons moving at nearly the speed of light in a relatively small radius orbit.

Synchrotrons

Main article: Synchrotron

To reach still higher energies, with relativistic mass approaching or exceeding the rest mass of the particles (for protons, billions of electron volts GeV), it is necessary to use a synchrotron. A synchrotron is a particular type of cyclic Particle accelerator in which the magnetic field (to turn the particles so they circulate and the electric field (to accelerate A synchrotron is a particular type of cyclic Particle accelerator in which the magnetic field (to turn the particles so they circulate and the electric field (to accelerate This is an accelerator in which the particles are accelerated in a ring of constant radius. An immediate advantage over cyclotrons is that the magnetic field need only be present over the actual region of the particle orbits, which is very much narrower than the diameter of the ring. (The largest cyclotron built in the US had a 184 in dia magnet pole, whereas the diameter of the LEP and LHC is nearly 10 km. The aperture of the beam of the latter was of the order of centimeters. )

However, since the particle momentum increases during acceleration, it is necessary to turn up the magnetic field B in proportion to maintain constant curvature of the orbit. In consequence synchrotrons cannot accelerate particles continuously, as cyclotrons can, but must operate cyclically, supplying particles in bunches, which are delivered to a target or an external beam in beam "spills" typically every few seconds. Note that since high energy synchrotrons do most of their work on particles that are already traveling at nearly the speed of light c, the time to complete one orbit of the ring is nearly constant, as is the frequency of the RF power needed to drive the acceleration.

Note also a further point about modern synchrotrons: because the beam aperture is small and the magnetic field does not cover the entire area of the particle orbit as it does for a cyclotron, several necessary functions can be separated. Instead of one huge magnet, one has a line of hundreds of bending magnets, enclosing (or enclosed by) vacuum connecting pipes. The focusing of the beam is handled independently by specialized quadrupole magnets, while the acceleration itself is accomplished in separate RF sections, rather similar to short linear accelerators. Quadrupole magnets consist of groups of four Magnets laid out so that in the Multipole expansion of the field the dipole terms cancel and where the lowest significant Also, there is no necessity that cyclic machines be circular, but rather the beam pipe may have straight sections between magnets where beams may collide. be cooled, etc.

Aerial photo of the Tevatron at Fermilab. The main accelerator is the ring above; the one below (about one-third the diameter, despite appearances) is for preliminary acceleration, beam cooling and storage, etc.
Aerial photo of the Tevatron at Fermilab. Tevatron is a circular Particle accelerator at the Fermi National Accelerator Laboratory in Batavia Illinois and is the highest energy particle collider Fermi National Accelerator Laboratory ( Fermilab) located in Batavia near Chicago, Illinois, is a U The main accelerator is the ring above; the one below (about one-third the diameter, despite appearances) is for preliminary acceleration, beam cooling and storage, etc.

More complex modern synchrotrons such as the Tevatron, LEP, and LHC (still under construction) may deliver the particle bunches into storage rings of magnets with constant B, where they can continue to orbit for long periods for experimentation or further acceleration. Tevatron is a circular Particle accelerator at the Fermi National Accelerator Laboratory in Batavia Illinois and is the highest energy particle collider A storage ring is a type of circular Particle accelerator in which a continuous or pulsed Particle beam may be kept circulating for a long period of time up to many The highest-energy machines such as the Tevatron and LHC are actually accelerator complexes, with a cascade of specialized elements in series, including linear accelerators for initial beam creation, one or more low energy synchrotrons to reach intermediate energy, storage rings where beams can be accumulated or "cooled" (reducing the magnet aperture required and permitting tighter focusing; see beam cooling), and a last large ring for final acceleration and experimentation. Stochastic cooling is a form of Particle beam cooling. It is used in some Particle accelerators and Storage rings to control the Emittance of

Electron synchrotrons

Segment of an electron synchrotron at DESY
Segment of an electron synchrotron at DESY

Circular electron accelerators fell somewhat out of favor for particle physics around the time that SLAC was constructed, because their synchrotron losses were considered economically prohibitive and because their beam intensity was lower than for the unpulsed linear machines. The DESY ( D eutsches E lektronen Sy nchrotron "German Electron Synchrotron" is the biggest German research center for Particle physics The Stanford Linear Accelerator Center ( SLAC) is a United States Department of Energy National Laboratory operated by Stanford University under The Cornell Electron Synchrotron, built at low cost in the late 1960s, was the first in a series of high-energy circular electron accelerators built for fundamental particle physics, culminating in the LEP at CERN.

A large number of electron synchrotrons have been built in the past two decades, specialized to be synchrotron light sources, of ultraviolet light and X rays; see below.

Storage rings

Main article: Storage ring

For some applications, it is useful to store beams of high energy particles for some time (with modern high vacuum technology, up to many hours) without further acceleration. A storage ring is a type of circular Particle accelerator in which a continuous or pulsed Particle beam may be kept circulating for a long period of time up to many This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner. This is especially true for colliding beam accelerators, in which two beams moving in opposite directions are made to collide with each other, with a large gain in effective collision energy. A collider is a type of a Particle accelerator involving directed beams of particles. Because relatively few collisions occur at each pass through the intersection point of the two beams, it is customary to first accelerate the beams to the desired energy, and then store them in storage rings, which are essentially synchrotron rings of magnets, with no significant RF power for acceleration.

Synchrotron radiation sources

Some circular accelerators have been built to deliberately generate radiation (called synchrotron light) as X-rays also called synchrotron radiation, for example the Diamond Light Source being built at the Rutherford Appleton Laboratory in England or the Advanced Photon Source at Argonne National Laboratory in Illinois, USA. This article is mostly concerned with applications of Synchrotron radiation. X-radiation (composed of X-rays) is a form of Electromagnetic radiation. Diamond Light Source is a Synchrotron research facility located in Oxfordshire, United Kingdom. The Rutherford Appleton Laboratory ( RAL) is a scientific research laboratory at Chilton near Didcot in Oxfordshire, England. England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland The Advanced Photon Source ( APS) at Argonne National Laboratory is a national Synchrotron -radiation light source research facility funded by the Argonne National Laboratory is one of the United States Department of Energy 's oldest and largest science and engineering research national laboratories and is The State of Illinois ( roughly ill-i-NOY is a state of the United States of America, the 21st to be admitted to the Union. High-energy X-rays are useful for X-ray spectroscopy of proteins or X-ray absorption fine structure (XAFS) for example. X-ray spectroscopy is a gathering name for several spectroscopic techniques for determining the electronic structure of materials by using X-ray excitation Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl X-ray absorption fine structure (XAFS is a specific structure observed in X-ray Absorption spectroscopy ( XAS)

Synchrotron radiation is more powerfully emitted by lighter particles, so these accelerators are invariably electron accelerators. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J Synchrotron radiation allows for better imaging as researched and developed at SLAC's SPEAR. The Stanford Linear Accelerator Center ( SLAC) is a United States Department of Energy National Laboratory operated by Stanford University under

History

Main article: List of accelerators in particle physics

Lawrence's first cyclotron was a mere 4 inches (100 mm) in diameter. A list of Particle accelerators used for Particle physics experiments Later he built a machine with a 60 in dia pole face, and planned one with a 184-inch dia, which was, however, taken over for WWII-related work connected with uranium isotope separation; after the war it continued in service for research and medicine over many years. A list of Particle accelerators used for Particle physics experiments World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including Isotope separation is the process of concentrating specific Isotopes of a Chemical element by removing other isotopes for example separating Natural uranium

The first large proton synchrotron was the Cosmotron at Brookhaven National Laboratory, which accelerated protons to about 3 GeV. The Cosmotron was a Particle accelerator, specifically a Proton Synchrotron, at Brookhaven National Laboratory. Brookhaven National Laboratory ( BNL) is a United States national laboratory located in Upton New York on Long Island, and was formally established The Bevatron at Berkeley, completed in 1954, was specifically designed to accelerate protons to sufficient energy to create anti-protons, and verify the particle-antiparticle symmetry of nature, then only strongly suspected. The Bevatron was a Particle accelerator &mdash specifically a weak-focusing proton Synchrotron &mdash at Lawrence Berkeley National Laboratory which In Particle physics and Quantum chemistry, antimatter is the extension of the concept of the Antiparticle to Matter, where antimatter is composed The Alternating Gradient Synchrotron (AGS) at Brookhaven was the first large synchrotron with alternating gradient, "strong focusing" magnets, which greatly reduced the required aperture of the beam, and correspondingly the size and cost of the bending magnets. The Alternating Gradient Synchrotron (AGS is a Particle accelerator - Collider complex located at the Brookhaven National Laboratory in Long Island In Accelerator physics strong focusing or alternating-gradient focusing is the principle that the net effect on a Particle beam of charged particles passing The Proton Synchrotron, built at CERN, was the first major European particle accelerator and generally similar to the AGS. The Proton Synchrotron (PS is the first major Particle accelerator at CERN, built as a 28 GeV Proton accelerator in the late 1950's and The European Organization for Nuclear Research (Organisation Européenne pour la Recherche Nucléaire known as CERN

The Fermilab Tevatron has a ring with a beam path of 4 miles (6 km). Fermi National Accelerator Laboratory ( Fermilab) located in Batavia near Chicago, Illinois, is a U Tevatron is a circular Particle accelerator at the Fermi National Accelerator Laboratory in Batavia Illinois and is the highest energy particle collider The largest circular accelerator ever built was the LEP synchrotron at CERN with a circumference 26. A synchrotron is a particular type of cyclic Particle accelerator in which the magnetic field (to turn the particles so they circulate and the electric field (to accelerate 6 kilometers, which was an electron/positron collider. The positrons or antielectron is the Antiparticle or the Antimatter counterpart of the Electron. It has been dismantled and the underground tunnel is being reused for a proton/antiproton collider called the LHC, due to start operation in at the end of July 2008. The aborted Superconducting Supercollider (SSC) in Texas would have had a circumference of 87 km. The Superconducting Super Collider ( SSC) would have been the world's largest and highest-energy Particle accelerator complex that was planned to be built mostly in Texas ( is a state geographically located in the South Central United States and is also known as the Lone Star State. Construction was started in 1991, but abandoned in 1993. Year 1991 ( MCMXCI) was a Common year starting on Tuesday (link will display full calendar of the Gregorian Calendar. Year 1993 ( MCMXCIII) was a Common year starting on Friday (link will display full 1993 Gregorian calendar) Very large circular accelerators are invariably built in underground tunnels a few metres wide to minimize the disruption and cost of building such a structure on the surface, and to provide shielding against intense secondary radiations that may occur. These are extremely penetrating at high energies.

Current accelerators such as the Spallation Neutron Source, incorporate superconducting cryomodules. The Spallation Neutron Source (SNS is an accelerator-based Neutron source being built in Oak Ridge Tennessee, USA by the U A cryomodule is that section or sections of a Linear particle accelerator composed of superconducting RF cavities used in a Linear accelerator, or linac The Relativistic Heavy Ion Collider, and upcoming Large Hadron Collider also make use of superconducting magnets and RF cavity resonators to accelerate particles. The Relativistic Heavy Ion Collider (RHIC pronounced like " Rick " ˈrɪk is a heavy- Ion Collider located at and operated by Brookhaven Superconductivity is a phenomenon occurring in certain Materials generally at very low Temperatures characterized by exactly zero electrical resistance A resonator is a device or system that exhibits Resonance or resonant behavior that is it naturally oscillates at some frequencies, called its resonance

Targets and detectors

The output of a particle accelerator can generally be directed towards multiple lines of experiments, one at a given time, by means of a deviating electromagnet. An electromagnet is a type of Magnet in which the Magnetic field is produced by the flow of an electric current. This makes it possible to operate multiple experiments without needing to move things around or shutting down the entire accelerator beam. Except for synchrotron radiation sources, the purpose of an accelerator is to generate high-energy particles for interaction with matter.

This is usually a fixed target, such as the phosphor coating on the back of the screen in the case of a television tube; a piece of uranium in an accelerator designed as a neutron source; or a tungsten target for an X-ray generator. A phosphor is a substance that exhibits the phenomenon of Phosphorescence (sustained glowing after exposure to energized particles such as Electrons Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the In a linac, the target is simply fitted to the end of the accelerator. The particle track in a cyclotron is a spiral outwards from the centre of the circular machine, so the accelerated particles emerge from a fixed point as for a linear accelerator.

For synchrotrons, the situation is more complex. Particles are accelerated to the desired energy. Then, a fast acting dipole magnet is used to switch the particles out of the circular synchrotron tube and towards the target.

A variation commonly used for particle physics research is a collider, also called a storage ring collider. Particle physics is a branch of Physics that studies the elementary constituents of Matter and Radiation, and the interactions between them A collider is a type of a Particle accelerator involving directed beams of particles. Two circular synchrotrons are built in close proximity - usually on top of each other and using the same magnets (which are then of more complicated design to accommodate both beam tubes). Bunches of particles travel in opposite directions around the two accelerators and collide at intersections between them. This can increase the energy enormously; whereas in a fixed-target experiment the energy available to produce new particles is proportional to the square root of the beam energy, in a collider the available energy is linear.

Higher energies

At present the highest energy accelerators are all circular colliders, but it is likely that limits have been reached in respect of compensating for synchrotron radiation losses for electron accelerators, and the next generation will probably be linear accelerators 10 times the current length. An example of such a next generation electron accelerator is the 40 km long International Linear Collider, due to be constructed between 2015-2020. The International Linear Collider ( ILC) is a proposed Linear particle accelerator.

As of 2005, it is believed that plasma wakefield acceleration in the form of electron-beam 'afterburners' and standalone laser pulsers will provide dramatic increases in efficiency within two to three decades. Plasma acceleration is a technique for accelerating Charged particles such as Electrons Positrons and Ions using an Electric field In plasma wakefield accelerators, the beam cavity is filled with a plasma (rather than vacuum). A short pulse of electrons or laser light either constitutes or immediately trails the particles that are being accelerated. The pulse disrupts the plasma, causing the charged particles in the plasma to integrate into and move toward the rear of the bunch of particles that are being accelerated. This process transfers energy to the particle bunch, accelerating it further, and continues as long as the pulse is coherent. [3]

Energy gradients as steep as 200 GeV/m have been achieved over millimeter-scale distances using laser pulsers[4] and gradients approaching 1 GeV/m are being produced on the multi-centimeter-scale with electron-beam systems, in contrast to a limit of about 0. 1 GeV/m for radio-frequency acceleration alone. Existing electron accelerators such as SLAC could use electron-beam afterburners to greatly increase the energy of their particle beams, at the cost of beam intensity. The Stanford Linear Accelerator Center ( SLAC) is a United States Department of Energy National Laboratory operated by Stanford University under Electron systems in general can provide tightly collimated, reliable beams; laser systems may offer more power and compactness. Thus, plasma wakefield accelerators could be used — if technical issues can be resolved — to both increase the maximum energy of the largest accelerators and to bring high energies into university laboratories and medical centres.

Black hole production

In the future, the possibility of black hole (BH) production at the highest energy accelerators may arise, if certain predictions of superstring theory are accurate. A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e See also String theory Superstring theory is an attempt to explain all of the particles and Fundamental forces of nature in one theory by modelling [5][6] These concerns have been particularly acute recently in connection with the LHC, which will begin operation in 2008. If they are produced, it is thought that black holes would evaporate extremely quickly via Bekenstein-Hawking radiation. Hawking radiation (also known as Bekenstein-Hawking radiation) is a Thermal radiation with a black body spectrum predicted to be emitted by Black holes However, the existence of the Bekenstein-Hawking radiation is controversial. [7] It is also thought that an analogy between colliders and cosmic rays demonstrates collider safety. If colliders can produce black holes, cosmic rays (and particularly ultra-high-energy cosmic rays, UHECRs) should have been producing them for eons, and they have yet to harm us. For the 1962 Bruce Conner film see Cosmic Ray (film Cosmic rays are energetic particles originating from space that impinge on In high-energy physics, an ultra-high-energy cosmic ray ( UHECR) or extreme-energy cosmic ray ( EECR) is a Cosmic ray (subatomic particle [8] However, to conserve energy and momentum, any BHs created in a collision between an UHECR and local matter would itself necessarily be produced moving at relativistic speed with respect to the Earth, and should therefore immediately escape into space, as its accretion and growth rate should be very slow. BHs produced in colliders (with components of equal mass) would have some chance of having a velocity less than Earth escape velocity, 11. 2 km per sec, and would be liable to capture and subsequent growth. The time scale for them to grow enough to be dangerous is likely to be very long (millions of years), but somewhat controversial.

See also

External links

Tandem accelerators

Amateur construction

References

  1. ^ how stuff works - atom smasher
  2. ^ BBC NEWS | Science/Nature | Secret 'dino bugs' revealed
  3. ^ Matthew Early Wright (April 2005). "Riding the Plasma Wave of the Future". Symmetry: Dimensions of Particle Physics (Fermilab/SLAC), p. 12.
  4. ^ Briezman, et al. "Self-Focused Particle Beam Drivers for Plasma Wakefield Accelerators. " (PDF) Retrieved 13 May 2005. Events 1497 - Pope Alexander VI excommunicates Girolamo Savonarola. Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar.
  5. ^ An Interview with Dr. Steve Giddings http://www.esi-topics.com/blackholes/interviews/SteveGiddings.html
  6. ^ Phys. Rev. D 66, 091901 (2002) http://prola.aps.org/abstract/PRD/v66/i9/e091901
  7. ^ Adam D. Helfer (2003). ""Do black holes radiate?" Rept. Prog. Phys. 66: 943.
  8. ^ R. Jaffe et al., Rev. Mod. Phys. 72, 1125–1140 (2000).

Dictionary

particle accelerator

-noun

  1. A device that accelerates electrically charged particles to extremely high speeds, for the purpose of inducing high energy reactions or producing high energy radiation.
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