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Stanford Synchrotron Lab steps out on its own

STANFORD -- Two February events at the Stanford Synchrotron Radiation Laboratory mark milestones in the evolution of synchrotron radiation.

Synchrotron radiation is intensely bright, highly concentrated light, in a spectrum from x-rays to ultraviolet. With wavelengths smaller than the distances between atoms and a beam that can be tuned to any point along a spectrum, researchers can use the light as a tool to study the arrangement of atoms in objects that are too small, thin, dilute or short-lived to be easily viewed by other means.

On Tuesday, Feb. 18, SSRL opened its doors as a full-time, stand-alone light source - one of only two high- energy synchrotron sources in the U.S. available for general scientific use.

An international list of more than 200 scientific teams has been waiting to use the lab's high-intensity beams of light to probe submolecular structures for studies in biology, chemistry, physics, and materials science. More than 100 experiments are scheduled for the lab's first three-month run.

And Feb. 24 through 27, SSRL and its parent laboratory, the Stanford Linear Accelerator Center, will be hosts to an International Workshop on Fourth Generation Light Sources. The conferees will plan a future, fourth generation of super-bright, specialized synchrotron light sources.

In the past, SSRL operated part-time each year, depending on SLAC's linear accelerator as a power source. The lab's beams of synchrotron light are a byproduct of high-energy physics experiments - the energy given off when electrons are forced to change speed or direction.

"SSRL's previous operational schedule led to the development of many different techniques for using synchrotron radiation," said the lab's director, physicist Arthur I. Bienenstock. "Steady operation will allow us to capitalize on those developments to support deep scientific research and important analytic utilization by academia, industry and government laboratories."

Bienenstock said that the workshop "marks an important stage in our planning for the accelerators of the 21st century, which will have much greater capabilities and will make entirely new, presently undreamed- of scientific research techniques possible."

SSRL research scientist Paul Phizackerly says that this light "is to x-rays what a laser is to a flashlight."

At SSRL, it has been used to find specific atoms in the complex hemoglobin molecule and to image heart arteries without coronary catheters. With an array of instruments available at the laboratory and brought in by researchers themselves, scientists focus its beamlines to study the function of catalysts, the electronic structure of materials and the structure of biological membranes.

The lab has been operating independently from SLAC for a year. During its 1991 startup run, a team of scientists from IBM and Bell Labs brought in specially miniaturized thin-film manufacturing equipment so they could watch in real time as a metallic film was layered atom by atom onto a computer chip. In the same run, members of SSRL's structural biology group continued work on methods to analyze the structure of a viral coat, an enzyme or other protein in minutes - work that until recently, took months or years to complete.

As one of the world's original "first generation" synchrotron radiation labs, the Stanford lab has been the testing ground for many of the concepts used in later developments of this scientific tool. Founded in 1973 to test the uses of "waste" energy from SLAC's linear accelerator, SSRL grew to surround SLAC's "SPEAR" electron storage ring, with 23 experiment stations used by 600 scientists from 180 institutions around the world. Its staff scientists became known for their expertise in uses of synchrotron light.

Since 1987, the lab has run only two to three months a year, because of incompatibilities between SLAC's physics experiments and SSRL's radiation beams. Now, after a $14 million Department of Energy-funded improvement project and a year of commissioning, the lab is operating full-time with its own source of high-speed electrons. A 3 billion- electron-volt (3GeV) particle injector pumps electrons into the SPEAR storage ring, which has been fully dedicated for synchrotron radiation use.

Operating in a new, low-emittance mode, the Stanford lab's electron beam now can produce some of the brightest, most concentrated x-rays currently available to science: a billion times brighter than the common x-ray tube.

This stand-alone capability makes SSRL a "second generation" synchrotron light source. It joins a handful of other such sources worldwide, including the National Synchrotron Light Source at Brookhaven, N.Y.

Over the years, scientists at SSRL have pioneered many of the techniques to tame, tune and intensify synchrotron rays. In 1987, working with SLAC scientists and the accelerator center's PEP (Positron Electron Project) electron storage ring, they produced the world's brightest X-ray beams - 100 billion times as bright as the common x-ray tube.

This brightness will not be achieved elsewhere until the mid-'90s, when new "third generation" synchrotron light sources are completed in Europe, Japan, at Lawrence Berkeley Laboratory and at Argonne National Laboratory in Illinois. The fourth generation, still in the conceptual stages, should be hundreds of thousands times brighter than those in use today.

An international group of scientists will discuss the technology for these still-brighter light sources during the workshop at the Stanford Linear Accelerator Center. Organized by Herman Winick, deputy director of SSRL, and Max Cornacchia, associate director of SSRL and head of its accelerator research operations, the workshop is sponsored by the U.S. Department of Energy.

The Stanford Synchrotron Radiation Laboratory and the Stanford Linear Accelerator Center are national laboratories, operated by the Department of Energy. The two labs have physically separated, but in October, 1992 they will merge administratively, to be operated under the same Energy Dept. contract. Staff arrangements will remain unchanged, with Bienenstock as director of SSRL and SLAC Director Burton Richter heading the whole complex.



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