BY DAWN LEVY

On Jan. 11, the Faculty Senate embarked on its first-ever field trip, meeting at the Stanford Linear Accelerator Center (SLAC) to hear a report from SLAC Director Jonathan Dorfan. The talk covered more than 20 years of SLAC achievements in 20 minutes and was followed by a tour of the government-owned, university-operated facility. The meeting gave faculty a quick and captivating look at key programs in high-energy physics, particle astrophysics and synchrotron radiation.

"We're studying the ultimate structure of matter," Dorfan told about 35 faculty members gathered in SLAC's W.K.H. Panofsky Auditorium. "What are the ultimate fundamental building blocks of nature? What are the forces that interact between those building blocks?"

At the head of a tour of SLAC's B Factory to study a physics process leading to more matter than antimatter in the Universe, John Hennessy jokes: “Hardhats -- for falling quarks!” photo: L.A. Cicero

SLAC's backbone is the linear accelerator, whose construction began in 1963 under the leadership of SLAC's first director, W.K.H. Panofsky. The first experiments at the Department of Energy-funded facility began in 1967.

Since then, SLAC has played an instrumental role in research ranging from cells to celestial bodies. About 100 faculty, 180 graduate students and 80 postdoctoral scholars from almost two dozen departments work there. In addition, more than 3,000 scientists from more than 25 nations work at SLAC, which is open to scientists worldwide who submit peer-reviewed proposals for research that is fundamental, unclassified and publishable. From 1995 to 2000, SLAC researchers generated about 700 publications annually.

An example of SLAC's role as a global resource is a five-nation collaboration led by physics Professor Peter Michelson to build a special telescope that will fly aboard a NASA satellite in 2005. Called GLAST, for Gamma Ray Large Area Space Telescope, the instrument will map the changing positions and intensities of celestial bodies over time.

"What distinguishes this large accelerator lab from all other big facilities in the world, in fact, is its association with a major research university," Dorfan said. "It has really been the reason that SLAC has been so successful."

At SLAC's "linac" (for linear accelerator), the world's highest-energy linear accelerator, Faculty Senate members heard how electrons are bunched and accelerated down a 2-mile pipe. At the end of their journey, electrons have about 1,000 times the energy of a lightning bolt.

"A very, very high-energy beam like this is able to resolve structures that are very, very small," Dorfan said. That makes the beam "essentially a very large and powerful electron microscope" capable of imaging objects about one-millionth the size of an atomic nucleus, he said.

"In the late '60s and the early '70s, Richard Taylor and company used this beam to look to see what was inside protons," Dorfan said. They found a proton is made of three fundamental building blocks called quarks. When they looked inside neutrons, they found three quark building blocks in a slightly different orientation.

Scientists also use magnets to guide subatomic particles through the Stanford Positron-Electron Asymmetric Ring (SPEAR) in ways that let them discover new particles, such as the tau lepton Martin Perl found in 1975. The discovery earned him a 1995 Nobel Prize.

SLAC engineers later built bigger rings to produce higher energies: the Positron-Electron Project (PEP-I), now being reconfigured as PEP-II, or the B Factory to make millions of particles called B mesons.

Faculty donned hardhats before entering the B Factory, which was designed to recreate, on a small scale, the initial conditions of the birth of the universe.

If the Big Bang created equal amounts of matter and antimatter, they would have annihilated each other. But the fact that matter exists indicates more matter than antimatter. The reason for the asymmetry may be a process called CP violation that physicists are attempting to create in PEP-II and detect with a 1,200-ton apparatus called BaBar. Through a NORAD-like control room, almost 600 scientists from nine countries remotely access data.

The last stop on the tour was the Stanford Synchrotron Radiation Laboratory (SSRL), whose multidisciplinary users employ synchrotron radiation, or ultra-intense X-ray beams produced when electrons accelerate around rings.

"When an electron goes around in a circle, it's very unhappy," Dorfan said. "It shows its unhappiness by emitting hard X-rays. Those hard X-rays are a gold mine for people in the material sciences, environmental science, biology, chemistry, et cetera."

That's because the higher the energy of the beam, the smaller the substance that can be imaged. Images of bone loss taken with synchrotron radiation have enabled researchers to better understand the role of estrogen in osteoporosis. Similarly, synchrotron images have enabled ultra-sensitive analysis of metal contaminants in silicon wafers -- a necessary advance for creation of next-generation integrated circuits.

Better imaging also allows improved measurement and characterization of environmental contaminants, said SSRL Professor Gordon Brown. In two weeks, SSRL scientists will receive samples from beneath leaking tanks at the Hanford nuclear storage site in Washington. SSRL data will guide risk assessment and remediation strategies.

Similarly, U.S. Geological Survey researcher Andrea Foster told faculty members about her use of the SSRL to study arsenic-contaminated drinking water in Bangladesh: "It affects 20 million people. Soil concentrations of arsenic are low. You can't detect them with traditional techniques."

The fastest-growing program at the synchrotron light source is in the field of structural molecular biology. One project aims to learn how bacteria infect mammalian cells by studying the structure of a protein called invasin. Explained Dorfan: "By characterizing invasin's 'footprint' and passing it on to a drug company, they can make an exact replica of that footprint. And when you get sick, you can take a medicine which will then block all of the sites where invasin would like to put down its footprint."

Another project advances the Human Genome Project: Now that the sequences of genes are known, scientists want to find out the functions of the proteins they encode by studying high-resolution protein structures.

While researchers learned a lot on their blitz through SLAC, they had fun too. Earlier at the pre-tour portion of the Faculty Senate meeting, Chair Brad Osgood had made a comment portending well for future field trips: "[Academic Secretary] Susan Schofield is not here today. She is unavoidably in Hawaii. That made me think that the next field trip we ought to take is to Hawaii. I'll talk to the provost about that, see what we can do."