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Stanford Report, October 9, 2002

SLAC: The first 40 years


On Oct. 2, scientists celebrated the 40th year of the Stanford Linear Accelerator Center (SLAC). It's a place that has advanced fundamental understanding of the physical world, from subatomic particles to outer space. But at 40, SLAC's not just for physicists anymore. It's also home of the first web server in America and the world's largest database. Its technologies have been used to zap cancer and map heart disease, to develop drugs that fit molecules like a key fits a lock, to pinpoint impurities that threaten the performance of silicon chips.

On April 10, 1956, Stanford staff met in Professor Wolfgang Panofsky's home to discuss Professor Robert Hofstadter's suggestion to build a linear accelerator that was at least 10 times as powerful as the Mark III, the third linear accelerator built at Stanford. It was nicknamed "The Monster" because it would need to be 2 miles long. Professor Edward Ginzton, who directed Stanford's microwave laboratory and went on to preside at Varian Associates, headed the project.

In 1957, university scientists presented a detailed proposal for construction of the linear accelerator, or "linac," on Stanford land. It would be the world's largest and most powerful atom smasher. In 1959, President Dwight D. Eisenhower announced his support for the proposal. Congress approved the plan in 1961: Stanford would operate SLAC under the direction of the Atomic Energy Commission (the forerunner of the U.S. Department of Energy).

The rest, they say, is history -- and SLAC even has the plaque designating it as a "National Historic Engineering Landmark" to prove it. SLAC is acknowledged as a world leader in the development of advanced accelerator techniques and high-powered klystrons -- devices that generate the microwaves for accelerating electrons. Incidentally, klystrons were invented at Stanford in 1937 by brothers Russell and Sigurd Varian utilizing an invention of Professor William Hansen (an electromagnetic cavity called a Rhumbatron). Though those inventions pre-date SLAC, for decades the center has advanced klystron technology, a critical component of both the SLAC 2-mile linac and of medical accelerators, which treat 100,000 cancer patients each day in the United States alone.

Following are select milestones in SLAC history.


In July on Stanford University lands in Menlo Park, construction begins on the largest physics project of its time -- the Stanford Linear Accelerator Center.


While excavating for SLAC, workers discover a nearly complete skeleton of a 10-foot marine mammal, Paleoparadoxia, which roamed Earth 14 million years ago. The fossil is donated to the Museum of Paleontology at the University of California-Berkeley in exchange for a plaster cast replica, which Panofsky's wife, Adele, assembles over nearly 20 years. In 1995, the replica is installed in SLAC's new Visitors' Center.


The linear accelerator, built by a team led by Panofsky, who joined the Stanford faculty in 1951 and directed SLAC from 1961 to 1985, is completed -- on time and within its $114 million budget. The lab's federal contract stipulates that classified research could be performed only should the university agree (it never has). Experiments begin to probe the structure of the proton and the neutron with electrons hurled at them from the linac. Scientists discover smaller particles within the proton and name them "quarks." The discovery eventually leads to a Nobel Prize (see 1990).


The Stanford Positron Electron Accelerating Ring (SPEAR) is completed, ushering in the era of particle colliders for the study of matter and antimatter. The ring, which stores counter-circulating electrons and positrons, is built under the leadership of then-Professor Burton Richter. It later provides data for two Nobel Prizes (see 1976 and 1995).


The Stanford Synchrotron Radiation Project (SSRP) is established with funding from the National Science Foundation, the U.S. Navy, Xerox Corp. and Bell Telephone Laboratories. Its operations begin in 1974, and in 1977 it is renamed the Stanford Synchrotron Radiation Laboratory (SSRL). At SSRL, scientists from diverse disciplines use synchrotron-produced X-rays and ultraviolet light beams to study matter at the atomic and molecular scale -- opening the door for a rich variety of studies in condensed-matter physics, materials science, chemistry and biochemistry. Stanford's Roger Kornberg, for example, used data collected at SSRL in determining the structure of RNA polymerase, a key enzyme governing how genes are transcribed into proteins.


Using a sophisticated detector at SPEAR to observe collisions between matter and antimatter, Richter, at Stanford since 1956, leads a team of physicists in discovery of a new particle called the J/psi particle, or charm quark. The discovery quickly earns a Nobel Prize (see 1976).


Using SPEAR, Professor Martin Perl discovers a new type of fundamental particle, the tau lepton, a heavy electron-like particle that is the first one found in a new third family of elementary particles. This discovery requires extending the Standard Model of particle physics theory to its current three-family form. The discovery eventually wins a Nobel Prize (see 1995).


Professor Burton Richter of SLAC and Samuel C. C. Ting of MIT are awarded a Nobel Prize "for their pioneering work in the discovery of a heavy elementary particle of a new kind."


In April, the Positron Electron Project (PEP) ring stores its first electron beam. PEP, a joint project of SLAC and the University of California's Lawrence Berkeley Laboratory, provides 10 times more energy than SPEAR and propels researchers into new territory, where evidence is found for gluons, the particles responsible for strong forces.


Construction begins on the Stanford Linear Collider (SLC), a novel machine for high-energy collisions of electrons and positrons. Its construction involves boring a 9,000-foot tunnel under the PEP tunnel, as well as extensively upgrading the 2-mile-long linear accelerator.


Richter is named SLAC's second director.


The SLC goes into operation, and experiments show that no more than three types of light neutrinos exist -- reinforcing the three-family form of the Standard Model of particle physics.


Professor Richard E. Taylor, at Stanford 1952-1958 and at SLAC 1962-present, is awarded a Nobel Prize with MIT's Jerome I. Friedman and Henry W. Kendall "for their pioneering investigations concerning deep inelastic scattering of electrons on protons and bound neutrons, which have been of essential importance for the development of the quark model in particle physics."


In September, SLAC physicist Paul Kunz visits CERN, the European particle physics center, where the web was invented as a tool to aid global physics collaborations. On Dec. 12, he brings the web to America by installing the first World Wide Web server outside of Europe on an IBM mainframe computer at SLAC. Physicists worldwide use it to retrieve information remotely from an important SLAC database. Within three years, browser improvements lead to an explosion of web use outside the scientific community.


SLAC Professor Martin Perl, at Stanford since 1963, is awarded a Nobel Prize "for the discovery of the tau lepton." He shares the award "for pioneering experimental contributions to lepton physics" with Frederick Reines of the University of California-Irvine, who is cited "for the detection of the neutrino."


Professor Jonathan Dorfan becomes SLAC's third director.


On Feb. 28, NASA announces an award to Stanford for development of a space-based telescope, the Gamma Ray Large Area Space Telescope (GLAST), scheduled to fly aboard a NASA satellite in 2005 and map the changing positions and intensities of celestial bodies over time. The telescope will be built as a collaboration of NASA, the Department of Energy and five countries, with project management centered at SLAC and Stanford physics Professor Peter Michelson as principal investigator.


In the summer, a collaboration of more than 600 scientists from 73 institutions in nine nations announces evidence for charge-parity, or CP, violation. This work, aimed at understanding why the universe contains more matter than antimatter, was done at SLAC's newest particle collider, the B Factory, whose construction began in 1994 as a PEP upgrade. Electrons and positrons collide inside a sophisticated, 1,200-ton particle detector called BABAR to create short-lived subatomic particles whose disintegration reveals subtle differences between matter and antimatter.

The Chen Particle Astrophysics and Cosmology Institute is established at SLAC with a $15 million donation from Pehong and Adele Chen. Pehong is founder and chief executive officer of BroadVision; his brother is SLAC physicist Pisin Chen.


SLAC is honored for creating the world's largest database, produced to support analysis of BABAR data.

The 'linac' is a 2-mile bridge into the unknown. When asked about SLAC's future, Pief Panofsky, the lab's first director, has always given the same reply: "SLAC will continue for about 10 more years unless someone has a good idea." Luckily for SLAC and Stanford, which enjoy a symbiotic relationship, "someone always did."