SLAC National Accelerator Laboratory

Menlo Park, California

SLAC Plaque Presentation

presentation of the plaque
Photo: SLAC National Accelerator Laboratory

APS past President Barry Barish (left) presented a plaque to SLAC National Accelerator Laboratory Director Persis Drell.

As part of the APS Historic Sites Initiative, on August 24, 2012, APS Past President Barry Barish presented a plaque to the SLAC National Accelerator Laboratory to commemorate its 50th anniversary as a premier facility in the area of particle physics. The plaque was accepted by laboratory Director Persis Drell. As written in the citation: "In recognition of the SLAC National Accelerator Laboratory, formerly Stanford Linear Accelerator Center, established 1962 and home of the 2-mile Stanford Linear Accelerator and the SPEAR electron storage ring. These two accelerators played an instrumental role in the discovery of quarks, the establishment of the Standard Model of particle physics, and the invention and use of high-brightness X-ray synchrotron and laser sources for the study of solid-state materials, surfaces, and biological structures."

Until 2008, the laboratory's official name was the Stanford Linear Accelerator Center, which refers to the world's highest energy linear accelerator. It originally operated at 17 GeV but later operated at energies as high as 48 GeV. Wolfgang K. H. Panofsky, the lab's first director, led the team that produced a machine so robust that it has been the workhorse of six generations of experiments on the frontier of science.

Beginning in 1967, SLAC carried out the "deep inelastic" electron-proton scattering experiments that revealed the structure of the proton as a bound state of quarks. These experiments gave a direct proof of the quark model, and the surprising weakness of quark interactions at short distances that they demonstrated turned out to be a crucial experimental clue leading to the discovery of Quantum Chromodynamics as the theory of the strong interactions. Jerome Friedman and Henry Kendall of MIT and Richard Taylor of SLAC led the experimental team and received the1990 Nobel Prize in physics for these discoveries.

Starting in 1972, SLAC operated the SPEAR electron-positron storage ring. This was not the first electron-positron collider, but its construction was a major advance in the accelerator art. SPEAR achieved record luminosities and the first demonstration of transverse beam polarization. The Mark I particle detector at SPEAR, built by a SLAC-Lawrence Berkeley Laboratory team led by Burton Richter, was the first detector designed for complete angular coverage of charged particles, photons and muons. Essentially all particle detectors at later generations of colliders were modeled on this design.

In 1974, the Mark I detector collaboration at SPEAR discovered the J/ψ (J/Psi) meson, announced simultaneously by Samuel Ting's group at MIT. In the next few years, the SPEAR group discovered additional S, P, and D-wave states of this particle-antiparticle spectrum. This established the identity of the J/ψ as a quark-antiquark bound state and crucially, made the quark model directly visualizable. Richter shared the 1976 Nobel Prize in Physics with Ting for his role in these discoveries.

Also in 1974, the Mark I detector collaboration discovered the heavy τ lepton. Martin Perl of SLAC received the 1995 Nobel Prize in Physics for recognizing and developing the evidence for the τ.

Beginning in 1972, SPEAR was used as the world's first storage-ring based synchrotron X-ray user facility, an innovation spearheaded by Sebastian Doniach and William Spicer. In the early 1970s experiments at SPEAR developed many of the innovative X-ray techniques that high-brightness synchrotrons would make possible, including XAFS spectroscopy and direct measurements of the changes in protein structure connected with biological function. Among the many discoveries made possible by the X-ray beams from SPEAR was the solution of the structure of RNA Polymerase II, for which Roger Kornberg of Stanford University was awarded the 2006 Nobel Prize in Chemistry.

Additional notable achievements at SLAC include:

  • The 1976 measurement of the left-right polarization asymmetry in deep elastic scattering, made by a team lead by SLAC's Charles Prescott, which was the last crucial clue that established the Glashow-Salam-Weinberg theory of weak interactions.
  • The operation as the world's first e+e- linear accelerator, beginning in 1989, which resulted in the first precise measurement of the Z0 boson mass and what is still the most precise measurement of the weak interaction mixing angle θw.
  • Rxperiments at SLAC's high-luminosity synchrotron PEP II, and parallel experiments at the KEK-B synchrotron at the KEK laboratory in Tsukuba, Japan, which observed time-dependent CP violation in rare decays of the B meson. These experiments, beginning in 2001, were essential in establishing the Kobayashi-Maskawa model, which explains the major CP violating phenomena in elementary particle dynamics.
  • The inauguration of the Linac Coherent Light Source (LCLS), the world's first hard X-ray laser in 2010. This new technique of Ångström-wavelength X-ray generation by a free-electron laser promises to usher in a new era of discovery in biological structure, quantum chemistry and other fields.  

1 Peskin, M. E., and Hodgson, K., Nomination Letter to Professor Benjamin Bederson, Chair, APS Historic Sites Committee, February 27, 2012.