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UCLA Team Seeking New Keys to Atoms' Inner Secrets

May 29, 1993|MARK A. STEIN | TIMES SCIENCE WRITER

Chan Joshi swiftly navigated the labyrinth of Boelter Hall's classrooms and offices toward his laboratory on the first floor of the UCLA engineering building. The cluttered, windowless room was dominated by a carbon-dioxide laser and the odd gear used to control it.

Off in one corner, away from the skillet-like copper mirrors and the portholes sliced from pure salt crystals, was a stainless steel chamber the size of a vacuum cleaner. Joshi and his graduate-student assistants posed behind it. This was where they taught electrons to surf.

In Texas, workers only recently began constructing the Superconducting Super Collider, and years will pass before the 54-mile-long, $10-billion science device can be switched on to try to answer some fundamental questions about atoms and the universe.

But Joshi and a handful of other scientists already are looking beyond the SSC and asking: What next?

Like superior chess players, these scientists are scrambling to stay several steps ahead of themselves. Their goal is to anticipate the methods and machines that would be needed to solve subatomic riddles no one has yet uncovered--riddles with solutions beyond the reach even of the mighty super collider, the biggest and costliest science device in history.

In his cramped laboratory, Joshi has demonstrated the feasibility of one of these machines, a new kind of particle accelerator. Unlike the super collider, which uses electrical fields to crack open relatively heavy protons, Joshi's device uses plasma waves to slam together lighter electrons.

His "beat-wave accelerator," based on a theory by fellow UCLA professor John Dawson, uses exquisitely timed laser pulses a few trillionths of a second long to shove electrons almost to the speed of light in a fraction of the space required by today's best particle accelerators.

With this technology, better particle accelerators would not necessarily have to be bigger. That is welcome news to policymakers still trying to sell a skeptical Congress on the value of a super collider the size of an entire county.

The laser pulses in Joshi's device create an electrically agitated gas, or plasma, rippling with very orderly waves. Electrons added at precisely the right instant tend to "surf" these waves, picking up speed the way people do when they ride ocean waves.

It is a delicate and complicated process that relies on notoriously unstable plasmas, Joshi conceded. But the experimental machine in his laboratory, while complex enough to be worthy of Rube Goldberg, shows that the idea works--indeed, he said, "it worked just as advertised."

And, Joshi added, the beat-wave accelerator has the ability to add speed to electrons more quickly than any other device, so a production model eventually may match the power of some of today's more powerful accelerators in a fraction of the space.

Whether this technology ever leaves the lab depends on whether Joshi and other researchers--beat-wave accelerators also are being developed in Japan, France and Britain--can increase both the size and power of their machines at a reasonable cost.

But even if they prove unable to do the kind of cutting-edge research expected of the super collider, beat-wave machines still can be useful, Joshi and Dawson said. Since they accelerate particles so much more quickly than conventional designs, powerful beat-wave machines could be relatively compact and easier to fit on more college campuses, making them more accessible.

Instead of one giant machine accommodating a few collaborative experiments--a process that forces many scientists to compromise their work--dozens of machines could be available to let individual researchers pursue their own theories. Accelerator time could be made as accessible as computer time was opened up when personal computers supplanted bulky mainframes.

In addition to benefiting researchers, this would make powerful accelerators accessible to more hospitals, where cell-killing particle beams from a few conventional machines already are used to combat cancer. Beat-wave machines also can be used to generate tiny bursts of light or x-rays that would permit better medical images using only a fraction of the radiation.

These electromagnetic "microbusts" also could allow scientists to make slow-motion movies of chemical reactions, which have never actually been seen before.

None of this occurred to Dawson when he dreamed up the idea of beat-wave particle accelerators while working at Princeton University in the 1970s. At the time, he was trying to use the coherent amplified light in laser beams to trigger temporary nuclear fusion reactions, but was frustrated when the laser created turbulence in the reactor's plasma fuel.

Once he worked out how the turbulence could be harnessed to accelerate electrons, potential applications were easy to think up, he said.

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