SLAC Linear Accelerator Center

The SLAC Linear Accelerator Center is one of the most prominent particle accelerators in the United States of America. It is a key research facility in the field of particle physics, with research from throughout the latter half of the twentieth century that has been recognized multiple times with awards such as the Nobel Prize in Physics.

SLAC is a high-energy linear accelerator, meaning that it is built in a straight line, as opposed to the circular rings used in many particle accelerators, including Fermilab and the Large Hadron Collider.

This linear accelerator is housed in a two-mile-long building, which is the third-longest building in the world and the longest building in America. (And by that, I include both North and South America, not merely the United States of America. The two longer buildings are the Great Wall in China and Pakistan’ Ranikot Fort.)

SLAC was built in 1962 at Stanford University, on ground leased to the United States Department of Energy. At the time it was built, the facility accelerated only electrons, but it was eventually upgraded to also include positrons. Various updates to the apparatus have been performed over the years, including the additions of particle accelerator rings which use the initial linear accelerator as a booster stage before sending the accelerated particles for collisions into the rings.

Origins of SLAC’s Name

The acronym SLAC originally stood for Stanford Linear Accelerator Center. In 2008, this was officially changed by the Department of Energy to “SLAC Linear Accelerator Center.” (Plausibly, as suggested by Sean Carroll, “Stanford didn’t want the Department of Energy to trademark an acronym containing their name.”)

Research at SLAC

In the 1970’s, a joint research effort by physicists from Stanford University and the Massachusetts Institute of Technology (MIT) used the electron beam from SLAC to explore the internal physical structure of the proton. This research resulted in the first direct experimental evidence that confirmed the theory that the proton itself was composed of smaller particles. The theory that protons were composite particles containing more fundamental components, called quarks, was already in circulation, but this evidence helped to advance the conviction among physicists that this theory was a correct model of particles. In addition to confirming the existence of the quarks, this also provided hints at another substance within the protons … the mysterious “glue” that held the quarks together, and ultimately came to be recognized as the gluon. This research resulted in the 1990 Nobel Prize in Physics for Jerome Friedman and Henry Kendall of MIT and Richard Taylor of SLAC.

In 1974, Burton Richter of SLAC announced a discovery of the J/psi particle, consisting of a charm quark paired with an anti-charm quark. This was independently discovered at nearly the same time by Samuel Chao Chung Ting of Brookhaven National Laboratory, and the two experimental physicists shared the 1976 Nobel Prize in Physics for the joint discovery.

SLAC physicist Martin L. Perl discovered the tau lepton in 1975, ultimately resulting in the 1995 Nobel Prize in Physics.

Since the 1970’s, SLAC’s scientific mission has gone from its initial role focused on exploration of particle physics to include research in cosmology, environmental science, biology, chemistry, materials science, and alternative energy research. Physicists from SLAC collaborate with scientists at facilities around the world, and a vast array of scientific disciplines utilize the various experimental apparatuses at SLAC to conduct their research.

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