Wednesday, September 28, 2011

SLAC - Stanford Linear Accelerator Center

The SLAC National Accelerator Laboratory, originally named Stanford Linear Accelerator Center,[1] [2] is a United States Department of Energy National Laboratoryoperated 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 inatomic and solid-state physicschemistrybiology, and medicine using synchrotron radiation.[3]



Founded in 1962 as the Stanford Linear Accelerator Center, 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 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.[7]
SLAC developed and, in December 1991, began hosting the first WWW server outside of Europe.[8]
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 physicists with doctorate degrees, and serves over 3,000 visiting researchers yearly, operatingparticle accelerators for high-energy physics and the Stanford Synchrotron Radiation Laboratory (SSRL) for synchrotron light radiation research,[3] which was "indispensable" in the research leading to the 2006 Nobel Prize in Chemistry.[9]
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".[1][10]


SLAC 1.9 mile (3 kilometer) long Klystron Gallery above the beamline Accelerator


The main accelerator is an RF linear accelerator that can accelerate electrons and positrons 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."[11] The main accelerator is buried 30 feet (about 10 meters) below ground[12]and passes underneath Interstate Highway 280. The above-ground klystron gallery atop the beamline is the longest building in the United States.
SLC pit and detector

Stanford Linear Collider

The Stanford Linear Collider was a linear accelerator that collided electrons and positrons at SLAC. The center of mass energywas 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.[13] 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.
Inside view of the SLD

[edit]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.


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 experiment, one of the so-called B-Factory experiments studying charge-parity symmetry.

Stanford Synchrotron Radiation Lightsource

The Stanford Synchrotron Radiation Lightsource (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 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.


SLAC plays host to part of the GLAST 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 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 partially housed on the grounds of SLAC, in addition to its presence on the main Stanford campus.


The Linac Coherent Light Source (LCLS) is a free electron laser 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.[14]
Aerial photo of the Stanford Linear Accelerator Center, with detector complex at the right (east) side
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.[15]

Other discoveries

  • SLAC has also been instrumental in the development of the klystron, a high-power microwave amplification tube.
  • There is active research on plasma acceleration with recent successes such as the doubling of the energy of 42 GeV electrons in a meter-scale accelerator.
  • There was a Paleoparadoxia found at the SLAC site, and its skeleton can be seen at a small museum there in the Breezeway.[16]
  • The SSRL facility was used to reveal hidden text in the Archimedes Palimpsest. 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.[17]

See also


  1. a b "SLAC renamed to SLAC Natl. Accelerator Laboratory"The Stanford Daily (The Stanford Daily Publishing Corporation). 2008-10-16. Retrieved 2008-10-16.
  2. ^ "Stanford Linear Accelerator Center renamed SLAC National Accelerator Laboratory / New Name Honors Successful Past, Launches a Future of Scientific Expansion". (press release), SLAC National Accelerator Laboratory. 2008-10-15. Archived from the original on 2011-07-20. Retrieved 2011-07-20.
  3. a b U.S. Department of Energy Office of Science (October 2005), Review of the Stanford Linear Accelerator Center Integrated Safety Management System: Final Report, Washington: United States Government Printing Office, p. 1
  4. ^ Nobel Prize in Physics 1976. Half prize awarded to Burton Richter.
  5. ^ Nobel Prize in Physics 1990 Award split between Jerome I. FriedmanHenry W. Kendall, and Richard E. Taylor.
  6. ^ Nobel Prize in Physics 1995 Half prize awarded to Martin L. Perl.
  7. ^ "Milestones:Stanford Linear Accelerator Center, 1962"IEEE Global History Network. IEEE. Retrieved 3 August 2011.
  8. ^ The Early World Wide Web at SLAC: Early Chronology and Documents
  9. ^ 2006 Nobel Prize in Chemistry : Synchrotron Radiation Laboratory at SLAC Contributes
  10. ^ A New Name for SLAC
  11. ^ Saracevic, Alan T. "Silicon Valley: It's where brains meet bucks.San Francisco Chronicle 23 October 2005. p J2. Accessed 2005-10-24.
  12. ^ Neal, R. B. (1968). "Chap. 5"The Stanford Two-Mile Accelerator. New York, New York: W.A. Benjamin, Inc. p. 59. Retrieved 2010-09-17.
  13. ^ John R. Rees, The Stanford Linear Collider, Scientific American 1989, 261:4 (October), pp. 36-43; see also a colleague's logbook at
  14. ^ Linac Coherent Light Source webpage
  15. ^ Rachel Ehrenberg,
  16. ^ Stanford's SLAC Paleoparadoxia much thanks to Adele Panofsky, Dr. Panofsky's wife, for her reassembly of the bones of the Paleoparadoxia uncovered at SLAC.
  17. ^ Bergmann, Uwe. "X-Ray Fluorescence Imaging of the Archimedes Palimpsest: A Technical Summary". SLAC National Accelerator Laboratory. Retrieved 2009-10-04.

External links

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