linear accelerator

or linac

Type of particle accelerator that imparts a series of relatively small increases in energy to subatomic particles as they pass through a sequence of alternating electric fields set up in a linear structure. The small accelerations add together to give the particles a greater energy than could be achieved by the voltage used in one section alone. One of the world's longest linacs is the 2-mi (3.2-km) machine at the Stanford Linear Accelerator Center, which can accelerate electrons to energies of 50 billion electron volts. Much smaller linacs, both proton and electron types, have important practical applications in medicine and industry.

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The Stanford Linear Accelerator Center (SLAC) 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. The 2.0 mile (3.2 kilometer) long underground accelerator is the longest linear accelerator in the world, and is claimed to be "the world's straightest object. SLAC's meeting facilities also provided a venue for the homebrew computer club and other pioneers of the 1980s home computer revolution, and later SLAC hosted the first webpage in the U.S. The above-ground klystron gallery atop the beamline is the longest building in the United States.


Founded in 1962, the facility is located on 426 acres (1.72 square kilometers) of Stanford University-owned land on Sand Hill Road in Menlo Park, California—just west from the University's main campus. The main accelerator, a 2.0 mile-long RF linear accelerator, which can accelerate electrons and positrons up to 50 GeV, has been operational since 1966. It is buried 30 feet (10 meters) below ground and passes underneath Interstate 280. As of 2005, SLAC employs over 1,000 people, some 150 of which are physicists with doctorate degrees, and serves over 3,000 visiting researchers yearly, operating particle accelerators for high-energy physics and the Stanford Synchrotron Radiation Laboratory (SSRL) for synchrotron light radiation research.

Research at SLAC has produced three Nobel Prizes in Physics:

Also, SSRL was "indispensable" in the research leading to the 2006 Nobel Prize in Chemistry.

In the early-to-mid 90s, the Stanford Linear Collider or SLC, investigated the properties of the Z boson using the Stanford Large Detector.

In the July, 2008 the Department of Energy announced it intends to change the name of SLAC. The reasons given include better representing the new direction of the lab and being able to trademark the name, which Stanford University legally opposes.

Stanford Linear Collider

The Stanford Linear Collider was a linear accelerator that collided electrons and positrons 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. The first Z event was recorded on April 12, 1989 by 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 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.

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.


Since 1999 the main purpose of the linear accelerator has been 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 experiment, one of the so-called B-Factory experiments studying charge-parity symmetry. The experiment was ended prematurely due to 2008 budget cuts.


SSRL is a synchrotron light user facility located on the SLAC campus. Originally built for particle physics, it was used in experiments where the J/Ψ particle particle was discovered. It is now used exclusively for materials science and biology experiments which take advantage of the high-intensity, monochromatic synchrotron radiation emitted by the stored electron beam to study the structure of molecules. In the 1980s, an independent electron injector was built for this storage ring, allowing it to operate independently of the main linear accelerator.


SLAC plays host to part of the GLAST project, a collaborative international project also known as The Gamma Ray Large Area Space Telescope, the principle objectives of which are:

  • To understand the mechanisms of particle acceleration in AGNs, pulsars, and SNRs.
  • 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.


The Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) is located on the grounds of SLAC.

Other discoveries

  • SLAC has also been instrumental in the development of the klystron, a high-power microwave amplification tube.
  • There was a Paleoparadoxia found at the SLAC site, and its skeleton can be seen at a small museum there in the Breezeway.
  • SLAC developed and hosted the first WWW server outside of Europe in December 1991 .


See also


External links

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