Stanford Linear Accelerator Center
Encyclopedia
The SLAC National Accelerator Laboratory, originally named Stanford Linear Accelerator Center, is a United States Department of Energy
National Laboratory
operated by Stanford University
under the programmatic direction of the U.S. Department of Energy Office of Science.
The SLAC research program centers on experimental
and theoretical
research in elementary
particle physics
using electron beams and a broad program of research in atomic
and solid-state physics, chemistry
, biology
, and medicine
using synchrotron radiation
.
-owned land on Sand Hill Road
in Menlo Park, California
—just west of the University's main campus. The main accelerator is 2 miles long—the longest linear accelerator in the world—and has been operational since 1966.
Research at SLAC has produced three Nobel Prizes in Physics
:
SLAC's meeting facilities also provided a venue for the Homebrew Computer Club
and other pioneers of the home computer
revolution of the late 1970s and early 1980s.
In 1984 the laboratory was named a ASME National Historic Engineering Landmark and an IEEE Milestone.
SLAC developed and, in December 1991, began hosting the first WWW server outside of Europe.
In the early-to-mid 1990s, the Stanford Linear Collider (SLC) investigated the properties of the Z boson using the Stanford Large Detector.
As of 2005, SLAC employs over 1,000 people, some 150 of which are physicist
s with doctorate degrees, and serves over 3,000 visiting researchers yearly, operating particle accelerator
s for high-energy physics and the Stanford Synchrotron Radiation Laboratory
(SSRL) for synchrotron light
radiation research, which was "indispensable" in the research leading to the 2006 Nobel Prize in Chemistry
.
In October 2008, the Department of Energy announced that the Center's name would be changed to SLAC National Accelerator Laboratory. The reasons given include a better representation of the new direction of the lab and the ability to trademark the laboratory's name. Stanford University had legally opposed the Department of Energy's attempt to trademark "Stanford Linear Accelerator Center".
that can accelerate electron
s and positron
s up to 50 GeV
. At 2.0 miles (about 3.2 kilometers) long, the accelerator
is the longest linear accelerator in the world, and is claimed to be "the world's straightest object." The main accelerator is buried 30 feet (about 10 meters) below ground and passes underneath Interstate Highway 280
. The above-ground klystron
gallery atop the beamline
is the longest building in the United States.
s and positron
s at SLAC. The center of mass
energy
was about 90 GeV
, equal to the mass
of the Z boson
, which the accelerator was designed to study.
Grad student Barrett D. Milliken discovered the first Z event
on 12 April 1989 while poring over the previous day's computer data from the Mark II detector. The bulk of the data was collected by the Stanford Large Detector, which came online in 1991. Although largely overshadowed by the Large Electron-Positron Collider at CERN
, which began running in 1989, the highly polarized electron beam at SLC (close to 80%) made certain unique measurements possible.
Presently no beam enters the south and north arcs in the machine, which leads to the Final Focus, therefore this section is mothballed to run beam into the PEP2 section from the beam switchyard.
, one of the so-called B-Factory
experiments studying charge-parity symmetry.
user facility located on the SLAC campus. Originally built for particle physics, it was used in experiments where the J/ψ meson was discovered. It is now used exclusively for materials science and biology experiments which take advantage of the high-intensity synchrotron radiation emitted by the stored electron beam to study the structure of molecules. In the early 1990s, an independent electron injector was built for this storage ring, allowing it to operate independently of the main linear accelerator.
project, a collaborative international project also known as Fermi Gamma-ray Space Telescope, the principle objectives of which are:
facility located at SLAC. The LCLS is partially a reconstruction of the last 1/3 of the original linear accelerator at SLAC, and can deliver extremely intense x-ray radiation for research in a number of areas. It achieved first lasing in April 2009.
The laser uses hard X-rays, 1×10^9 the relative brightness of traditional synchotron X-rays, in order to take "snapshots" of objects on the nearly atomic level before obliterating samples. The laser's wavelength is similar in width to an atom, providing extremely detailed images on a scale previously unattainable. Additionally, the laser is capable of capturing images with a "shutter speed" measured in femtoseconds, or trillionths of a second, necessary because the intensity of the beam is such that it nearly instantly destroys its subject.
United States Department of Energy
The United States Department of Energy is a Cabinet-level department of the United States government concerned with the United States' policies regarding energy and safety in handling nuclear material...
National Laboratory
United States Department of Energy National Laboratories
The United States Department of Energy National Laboratories and Technology Centers are a system of facilities and laboratories overseen by the United States Department of Energy for the purpose of advancing science and helping promote the economic and defensive national interests of the United...
operated by Stanford University
Stanford University
The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...
under the programmatic direction of the U.S. Department of Energy Office of Science.
The SLAC research program centers on experimental
Experimental physics
Within the field of physics, experimental physics is the category of disciplines and sub-disciplines concerned with the observation of physical phenomena in order to gather data about the universe...
and theoretical
Theoretical physics
Theoretical physics is a branch of physics which employs mathematical models and abstractions of physics to rationalize, explain and predict natural phenomena...
research in elementary
Elementary particle
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 up of smaller particles. If an elementary particle truly has no substructure, then it is one of the basic building blocks of the universe from which...
particle physics
Particle physics
Particle physics is a branch of physics that studies the existence and interactions of particles that are the constituents of what is usually referred to as matter or radiation. In current understanding, particles are excitations of quantum fields and interact following their dynamics...
using electron beams and a broad program of research in atomic
Atomic physics
Atomic physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. It is primarily concerned with the arrangement of electrons around the nucleus and...
and solid-state physics, chemistry
Chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....
, biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
, and medicine
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
using synchrotron radiation
Synchrotron radiation
The electromagnetic radiation emitted when charged particles are accelerated radially is called synchrotron radiation. It is produced in synchrotrons using bending magnets, undulators and/or wigglers...
.
History
Founded in 1962 as the Stanford Linear Accelerator Center, the facility is located on 426 acres (1.72 square kilometers) of Stanford UniversityStanford University
The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...
-owned land on Sand Hill Road
Sand Hill Road
Sand Hill Road is a road in Menlo Park, California, notable for its concentration of venture capital companies. Its significance as a symbol of private equity in the United States may be compared to that of Wall Street in the stock market...
in Menlo Park, California
Menlo Park, California
Menlo Park, California is a city at the eastern edge of San Mateo County, in the San Francisco Bay Area of California, in the United States. It is bordered by San Francisco Bay on the north and east; East Palo Alto, Palo Alto, and Stanford to the south; Atherton, North Fair Oaks, and Redwood City...
—just west of the University's main campus. The main accelerator is 2 miles long—the longest linear accelerator in the world—and has been operational since 1966.
Nobel Prize in Physics
The Nobel Prize in Physics is awarded once a year by the Royal Swedish Academy of Sciences. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895 and awarded since 1901; the others are the Nobel Prize in Chemistry, Nobel Prize in Literature, Nobel Peace Prize, and...
:
- 1976: The charm quarkCharm quarkThe charm quark or c quark is the third most massive of all quarks, a type of elementary particle. Charm quarks are found in hadrons, which are subatomic particles made of quarks...
—see J/ψ meson - 1990: QuarkQuarkA quark is an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. Due to a phenomenon known as color confinement, quarks are never directly...
structure inside protonProtonThe proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....
s and neutronNeutronThe neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
s - 1995: The tau leptonTau leptonThe tau , also called the tau lepton, tau particle or tauon, is an elementary particle similar to the electron, with negative electric charge and a spin of . Together with the electron, the muon, and the three neutrinos, it is classified as a lepton...
SLAC's meeting facilities also provided a venue for the Homebrew Computer Club
Homebrew Computer Club
The Homebrew Computer Club was an early computer hobbyist users' group in Silicon Valley, which met from March 5, 1975 to December 1986...
and other pioneers of the home computer
Home computer
Home computers were a class of microcomputers entering the market in 1977, and becoming increasingly common during the 1980s. They were marketed to consumers as affordable and accessible computers that, for the first time, were intended for the use of a single nontechnical user...
revolution of the late 1970s and early 1980s.
In 1984 the laboratory was named a ASME National Historic Engineering Landmark and an IEEE Milestone.
SLAC developed and, in December 1991, began hosting the first WWW server outside of Europe.
In the early-to-mid 1990s, the Stanford Linear Collider (SLC) investigated the properties of the Z boson using the Stanford Large Detector.
As of 2005, SLAC employs over 1,000 people, some 150 of which are physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
s with doctorate degrees, and serves over 3,000 visiting researchers yearly, operating particle accelerator
Particle accelerator
A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator. There are two basic types: electrostatic and oscillating field accelerators.In...
s for high-energy physics and the Stanford Synchrotron Radiation Laboratory
Stanford Synchrotron Radiation Laboratory
The Stanford Synchrotron Radiation Lightsource , a division of SLAC National Accelerator Laboratory, is operated by Stanford University for the Department of Energy...
(SSRL) for synchrotron light
Synchrotron light
A synchrotron light source is a source of electromagnetic radiation produced by a synchrotron, which is artificially produced for scientific and technical purposes by specialized particle accelerators, typically accelerating electrons...
radiation research, which was "indispensable" in the research leading to the 2006 Nobel Prize in Chemistry
Nobel Prize in Chemistry
The Nobel Prize in Chemistry is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of chemistry. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895, awarded for outstanding contributions in chemistry, physics, literature,...
.
In October 2008, the Department of Energy announced that the Center's name would be changed to SLAC National Accelerator Laboratory. The reasons given include a better representation of the new direction of the lab and the ability to trademark the laboratory's name. Stanford University had legally opposed the Department of Energy's attempt to trademark "Stanford Linear Accelerator Center".
Components
Accelerator
The main accelerator is an RF linear acceleratorLinear particle accelerator
A linear particle accelerator is a type of particle accelerator that greatly increases the velocity of charged subatomic particles or ions by subjecting the charged particles to a series of oscillating electric potentials along a linear beamline; this method of particle acceleration was invented...
that can accelerate electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s and positron
Positron
The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1e, a spin of ½, and has the same mass as an electron...
s up to 50 GeV
GEV
GEV or GeV may stand for:*GeV or gigaelectronvolt, a unit of energy equal to billion electron volts*GEV or Grid Enabled Vehicle that is fully or partially powered by the electric grid, see plug-in electric vehicle...
. At 2.0 miles (about 3.2 kilometers) long, the accelerator
Particle accelerator
A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator. There are two basic types: electrostatic and oscillating field accelerators.In...
is the longest linear accelerator in the world, and is claimed to be "the world's straightest object." The main accelerator is buried 30 feet (about 10 meters) below ground and passes underneath Interstate Highway 280
Interstate 280 (California)
Interstate 280 is a 57-mile long north–south Interstate Highway in the San Francisco Bay Area of Northern California. It connects San Jose and San Francisco, running along just to the west of the cities of San Francisco Peninsula for most of its route.I-280 from its northern end at King...
. The above-ground klystron
Klystron
A klystron is a specialized linear-beam vacuum tube . Klystrons are used as amplifiers at microwave and radio frequencies to produce both low-power reference signals for superheterodyne radar receivers and to produce high-power carrier waves for communications and the driving force for modern...
gallery atop the beamline
Beamline
In particle physics, a beamline is the line in a linear accelerator along which a beam of particles travels. It may also refer to the line of travel within a bending section such as a storage ring or cyclotron, or an external beam extracted from a cyclic accelerator.In materials science, physics,...
is the longest building in the United States.
Stanford Linear Collider
The Stanford Linear Collider was a linear accelerator that collided electronElectron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s and positron
Positron
The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1e, a spin of ½, and has the same mass as an electron...
s at SLAC. The center of mass
Center of mass
In physics, the center of mass or barycenter of a system is the average location of all of its mass. In the case of a rigid body, the position of the center of mass is fixed in relation to the body...
energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...
was about 90 GeV
GEV
GEV or GeV may stand for:*GeV or gigaelectronvolt, a unit of energy equal to billion electron volts*GEV or Grid Enabled Vehicle that is fully or partially powered by the electric grid, see plug-in electric vehicle...
, equal to the mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
of the Z boson
W and Z bosons
The W and Z bosons are the elementary particles that mediate the weak interaction; their symbols are , and . The W bosons have a positive and negative electric charge of 1 elementary charge respectively and are each other's antiparticle. The Z boson is electrically neutral and its own...
, which the accelerator was designed to study.
Grad student Barrett D. Milliken discovered the first Z event
Event (particle physics)
An event in particle physics describes one set of particle interactions occurring in a brief span of time, typically recorded together. At modern particle accelerators this refers to the interactions that occur as a result of one beam crossing inside a detector....
on 12 April 1989 while poring over the previous day's computer data from the Mark II detector. The bulk of the data was collected by the Stanford Large Detector, which came online in 1991. Although largely overshadowed by the Large Electron-Positron Collider at CERN
CERN
The European Organization for Nuclear Research , known as CERN , is an international organization whose purpose is to operate the world's largest particle physics laboratory, which is situated in the northwest suburbs of Geneva on the Franco–Swiss border...
, which began running in 1989, the highly polarized electron beam at SLC (close to 80%) made certain unique measurements possible.
Presently no beam enters the south and north arcs in the machine, which leads to the Final Focus, therefore this section is mothballed to run beam into the PEP2 section from the beam switchyard.
Stanford Large Detector
The Stanford Large Detector (SLD) was the main detector for the Stanford Linear Collider. It was designed primarily to detect Z bosons produced by the accelerator's electron-positron collisions. The SLD operated from 1992 to 1998.PEP-II
From 1999 to 2008, the main purpose of the linear accelerator was to inject electrons and positrons into the PEP-II accelerator, an electron-positron collider with a pair of storage rings 1.4 miles (2.2 km) in circumference. PEP-II was host to the BaBar experimentBaBar experiment
The BaBar experiment, or simply BaBar, is an international collaboration of more than 500 physicists and engineers studying the subatomic world at energies of approximately ten times the rest mass of a proton . Its design was motivated by the investigation of CP violation...
, one of the so-called B-Factory
B-Factory
In particle physics, a B-factory, or sometimes a beauty factory, is a collider-based scientific machine designed to produce a large number of B mesons and analyze their properties. The tauons and D mesons are also copiously produced at B-factories, which allows precise studies of their...
experiments studying charge-parity symmetry.
Stanford Synchrotron Radiation Lightsource
The Stanford Synchrotron Radiation Lightsource (SSRL) is a synchrotron lightSynchrotron light
A synchrotron light source is a source of electromagnetic radiation produced by a synchrotron, which is artificially produced for scientific and technical purposes by specialized particle accelerators, typically accelerating electrons...
user facility located on the SLAC campus. Originally built for particle physics, it was used in experiments where the J/ψ meson was discovered. It is now used exclusively for materials science and biology experiments which take advantage of the high-intensity synchrotron radiation emitted by the stored electron beam to study the structure of molecules. In the early 1990s, an independent electron injector was built for this storage ring, allowing it to operate independently of the main linear accelerator.
GLAST
SLAC plays host to part of the GLASTGamma-ray Large Area Space Telescope
The Fermi Gamma-ray Space Telescope , formerly referred to as the “Gamma-ray Large Area Space Telescope ”, is a space observatory being used to perform gamma-ray astronomy observations from low Earth orbit...
project, a collaborative international project also known as Fermi Gamma-ray Space Telescope, the principle objectives of which are:
- To understand the mechanisms of particle acceleration in AGNsActive galactic nucleusAn active galactic nucleus is a compact region at the centre of a galaxy that has a much higher than normal luminosity over at least some portion, and possibly all, of the electromagnetic spectrum. Such excess emission has been observed in the radio, infrared, optical, ultra-violet, X-ray and...
, pulsars, and SNRsSupernova remnantA supernova remnant is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar material it sweeps up and shocks along the way.There are two...
. - Resolve the gamma-ray sky: unidentified sources and diffuse emission.
- Determine the high-energy behavior of gamma-ray bursts and transients.
- Probe dark matter and early Universe.
KIPAC
The Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) is partially housed on the grounds of SLAC, in addition to its presence on the main Stanford campus.LCLS
The Linac Coherent Light Source (LCLS) is a free electron laserFree electron laser
A free-electron laser, or FEL, is a laser that shares the same optical properties as conventional lasers such as emitting a beam consisting of coherent electromagnetic radiation which can reach high power, but which uses some very different operating principles to form the beam...
facility located at SLAC. The LCLS is partially a reconstruction of the last 1/3 of the original linear accelerator at SLAC, and can deliver extremely intense x-ray radiation for research in a number of areas. It achieved first lasing in April 2009.
Other discoveries
- SLAC has also been instrumental in the development of the klystronKlystronA klystron is a specialized linear-beam vacuum tube . Klystrons are used as amplifiers at microwave and radio frequencies to produce both low-power reference signals for superheterodyne radar receivers and to produce high-power carrier waves for communications and the driving force for modern...
, a high-power microwaveMicrowaveMicrowaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
amplification tube. - There is active research on plasma accelerationPlasma accelerationPlasma Wakefield acceleration is a technique for accelerating charged particles, such as electrons, positrons and ions, using an electric field associated with an electron plasma wave. The wave is created either using electron pulses or through the passage of a very brief laser pulses, a technique...
with recent successes such as the doubling of the energy of 42 GeV electrons in a meter-scale accelerator. - There was a PaleoparadoxiaPaleoparadoxiaPaleoparadoxia is a genus of large, herbivorous marine mammals that inhabited the northern Pacific coastal region during the Miocene epoch . It ranged from the waters of Japan , to Alaska to the north, and down to Baja California, Mexico...
found at the SLAC site, and its skeleton can be seen at a small museum there in the Breezeway. - The SSRL facility was used to reveal hidden text in the Archimedes PalimpsestArchimedes PalimpsestThe Archimedes Palimpsest is a palimpsest on parchment in the form of a codex. It originally was a copy of an otherwise unknown work of the ancient mathematician, physicist, and engineer Archimedes of Syracuse and other authors, which was overwritten with a religious text.Archimedes lived in the...
. X-rays from the synchrotron radiation lightsource caused the iron in the original ink to glow, allowing the researchers to photograph the original document that a Christian monk had scrubbed off.
See also
- Accelerator physicsAccelerator physicsAccelerator physics deals with the problems of building and operating particle accelerators.The experiments conducted with particle accelerators are not regarded as part of accelerator physics. These belong to particle physics, nuclear physics, condensed matter physics, materials physics, etc...
- BeamlineBeamlineIn particle physics, a beamline is the line in a linear accelerator along which a beam of particles travels. It may also refer to the line of travel within a bending section such as a storage ring or cyclotron, or an external beam extracted from a cyclic accelerator.In materials science, physics,...
- CERNCERNThe European Organization for Nuclear Research , known as CERN , is an international organization whose purpose is to operate the world's largest particle physics laboratory, which is situated in the northwest suburbs of Geneva on the Franco–Swiss border...
- CyclotronCyclotronIn technology, a cyclotron is a type of particle accelerator. In physics, the cyclotron frequency or gyrofrequency is the frequency of a charged particle moving perpendicularly to the direction of a uniform magnetic field, i.e. a magnetic field of constant magnitude and direction...
- Dipole magnetDipole magnetA dipole magnet, in particle accelerators, is a magnet constructed to create a homogeneous magnetic field over some distance. Particle motion in that field will be circular in a plane perpendicular to the field and collinear to the direction of particle motion and free in the direction orthogonal...
- ElectromagnetismElectromagnetismElectromagnetism is one of the four fundamental interactions in nature. The other three are the strong interaction, the weak interaction and gravitation...
- List of particles
- List of United States college laboratories conducting basic defense research
- Particle beamParticle beamA particle beam is a stream of charged or neutral particles which may be directed by magnets and focused by electrostatic lenses, although they may also be self-focusing ....
- Particle physicsParticle physicsParticle physics is a branch of physics that studies the existence and interactions of particles that are the constituents of what is usually referred to as matter or radiation. In current understanding, particles are excitations of quantum fields and interact following their dynamics...
- Quadrupole magnetQuadrupole magnetQuadrupole 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 terms in the field equations are quadrupole. Quadrupole magnets are useful as they create a magnetic field whose magnitude grows...
- Spallation Neutron SourceSpallation Neutron SourceThe Spallation Neutron Source is an accelerator-based neutron source facility that provides the most intense pulsed neutron beams in the world for scientific research and industrial development...
- Wolfgang Panofsky (1961–84, SLAC Director; Professor, Stanford University)
External links
- SLAC official webpage
- SLAC Today, SLAC's online newspaper, published weekdays
- symmetry magazine, SLAC's monthly particle physics magazine, with FermilabFermilabFermi National Accelerator Laboratory , located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics...