SLAC unveils new accelerator SLAC unveils new accelerator (February 04, 2004)

By Marion Softky

Almanac Staff Writer

With snaking orange cables and bright-colored magnets, SLAC's newest accelerator still has that new-car smell.

Starting in March, SPEAR3 -- dedicated last week at the Stanford Linear Accelerator Center -- will provide a new, powerful source of X-rays where scientists from around the world can study the inner structure of matter and devise applications, from drugs to more powerful computer chips or anti-pollution devices.

"The future is bright," said Stanford Professor Keith Hodgson, director of the new facility, called the Stanford Synchrotron Radiation Laboratory -- SSRL for short. "SPEAR3 is a remarkable resource that will allow state-of-the-art science in numerous fields."

A total rebuild of SPEAR2, the new accelerator provides a form of X-rays called synchrotron radiation. These X-rays, which spin off when electrons are steered in a circle, can be focused into high-intensity beams. It's a little like the way a bicycle tire sprays rainwater as it spins, says Neil Calder, SLAC's communications officer.

Some 2,000 scientists from around the world will use the X-ray beams generated in SPEAR3 to bombard samples and study their properties. Because the beams are 10 billion times brighter than conventional X-ray sources, and 100 times brighter than those produced by SPEAR2, researchers will be able to take data faster, and study smaller objects in greater detail, said Mr. Calder.

SSRL houses many of the more practical applications of research performed for more than 40 years among the gentle hills south of Sand Hill Road in unincorporated Menlo Park. SLAC is more famous for fundamental studies on the nature of matter and the origin of the universe. These are performed with the two-mile linear accelerator and other accelerators that smash electrons and positrons together at the speed of light, creating weird particles and shedding light on what makes matter work.

SPEAR3 is the second reinvention of the original SPEAR, which served as a model for larger, more powerful colliding rings tunneled into the hills. Research on the first SPEAR -- a quarter of a kilometer long -- produced two Nobel prizes for discovery of new particles: the charm quark and the tau lepton. SPEAR stands for Stanford Positron Electron Asymmetric Ring.

For 30 years SPEAR2 has been harvesting X-rays from the rotating electron beam, and using them for research. The visitors center at SLAC displays examples of practical results from SPEAR2, such as telling photos of bone loss from osteoporosis.
Recycling SPEAR

SPEAR3 is a total replacement of SPEAR2. The 11-month project involved dismantling and removing the entire accelerator; removing and replacing the concrete floor with 700 cubic yards of new concrete; and building a completely new accelerator with 68 miles of cable and 290 magnets, all precisely aligned.

Officials at the dedication said they were proud that the $58 million project was done on time and in budget. SPEAR3 was jointly funded by the Department of Energy, which oversees SLAC, and the National Institutes of Health.

"We're very happy," said Ed Guerra, operations manager for SPEAR3, as he explained the daunting array of cables, magnets, beam tubes, wigglers, undulators, and other shiny equipment with the new-car smell in the SPEAR tunnel. SPEAR3 has already operated at 100 milli-amperes of current, he said. By March it should produce 500 milli-amps.

At one of the experiment stations outside the SPEAR3 ring, staff scientist Mitchell Miller was working with apparatus that will use the SPEAR3 beam to study the growth of protein crystals important in understanding DNA and RNA, molecules that are key to life.

Actually, Mr. Miller can do a lot of his work from his home, thanks to the automation being built into the experiments.

Where does he live and mostly work?

"Houston," he replies.

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