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Persis Highlights SLAC Science at Women in Science Speaker Series

At a luncheon given in her honor by the American Committee for the Weizmann Institute of Science last week, SLAC Director Persis Drell highlighted the evolution of research at the lab and described work at its flagship facility, the Linac Coherent Light Source—the world's most powerful X-ray free-electron laser.

Why does the LCLS use X-rays to examine matter? Drell flashed a slide onto the screen at the Stanford Park Hotel meeting room: an X-ray taken of her son, years ago, after he swallowed a quarter. We're familiar with the way conventional X-rays penetrate the human body to reveal bones, organs, even coins; but the LCLS's ultra-intense, short-wavelength X-ray laser pulses go far beyond that, showing scientists where the atoms in a material are—its structure—and where their electrons are, which together determine the material's properties and functions.

Another slide: A famous series of photos taken by Eadweard Muybridge in 1878, proving that during a gallop a horse lifts all four feet off the ground at once. In similar fashion, Drell said, scientists will use the LCLS as an X-ray camera with a very fast shutter speed—measured in millionths of a billionth of a second—to make stop-motion movies of atoms and electrons moving on their natural timescales.

Researchers have already used the LCLS to make the first images of an intact virus and confirm the structure of a protein from tiny nanocrystals, rather than the much larger protein crystals required today. Eventually, Drell said, they hope to resolve the structures of whole, unaltered molecules, cells and microbes by blasting the samples with X-ray pulses. This vaporizes the fragile samples; but in the instant before that happens, enough X-rays scatter off the sample to form a pattern in a detector, and scientists can use that pattern to reconstruct the sample's structure. To get a feel for how challenging these reconstructions are, she said, imagine dropping a very odd-shaped rock into a swimming pool and using the pattern of ripples arriving at the edge of the pool to reconstruct the rock.

Scientists are in the early stages of exploring what this first-of-its kind facility can do. About a thousand scientists have used the LCLS since it opened in late 2009, and time on the machine is in such demand that the expert panels that review each research proposal can schedule beam time for only about one out of five of them, she said, adding, "Every one of us is convinced that the biggest surprises are yet to come."

The talk was part of the Weizmann Women in Science Speaker Series, which honors the Bay Area's top women in research, biotechnology, high technology and health care. It benefits the Bay Area Fund for Women Scientists at the Weizmann Institute of Science.

Suzy Locke Cohen, who sits on the regional board of the American Committee for the Weizmann, said the Israeli institute has dramatically increased the number of women it hires into senior scientist positions. From 2000 to 2006 only 3 percent of these jobs went to women; from 2006 to this year, 30 percent of hires were women.

Nonetheless, it is still a struggle for women at the institute to move beyond their PhD studies into the postdoctoral research that is a vital stage of a career in science, said Weizmann Professor Yaron Silberberg, who is visiting SLAC for six months. Because Israel is such a small country, he said, scientists must go abroad for their postdoctoral studies, and it is especially hard for women to uproot their families to do that. The Bay Area Fund for Women Scientists offers support to women during their years abroad and at other stages of their academic careers.

—Glennda Chui
  SLAC Today, May 19, 2011