Printer Friendly

Potent laser twirls electron figure eights.

During the past decade, experimenters have developed laser beams of unprecedented power. Like other forms of light, these beams are composed of perpendicular electric and magnetic fields. The laser beams' enormously strong electric fields tear electrons from atoms and accelerate the freed particles almost instantly to nearly the speed of light. Made more intense each year, compact lasers have promised to unlock new areas of physics and usher in practical advances such as X-ray lasers and tabletop particle accelerators (SN: 9/5/98, p. 157).

In a partial fulfillment of that promise, researchers at the University of Michigan in Ann Arbor report a laser experiment confirming a 30-year-old prediction based on Einstein's theory of relativity.

The Michigan findings indicate that high-power, short-pulse lasers have reached sufficient intensities for "opening up a whole new regime" of physics, says Nicolaas Bloembergen of Harvard University, who shared the 1981 Nobel Prize in Physics for pioneering studies using lasers to probe atoms.

As described in the Dec. 17 NATURE, Michigan researchers Szu-yuan Chen, Anatoly Maksimchuk, and Donald Umstadter fired 4-trillion-watt laser bursts lasting less than a half-trillionth second. The bursts tore their target, helium gas, into a plasma of electrons and ions.

Theorists predicted in the 1960s that a laser's magnetic field, which has no effect on low-speed electrons, would exert a force on the fast-moving electrons accelerated by the laser electric field. Because the magnetic field pushes perpendicularly to the electric field, the oscillating fields would force the particles into minuscule figure eights.

Electrons on that swooping trajectory would re-emit light at the frequency of the laser itself but also, more importantly, at harmonics of the laser's frequency. The Michigan team reports that they detected those telltale harmonics.

Moreover, a digital camera showed that the emissions emerged in a cloverleaf pattern, as predicted. "The figure eight [motion] is inferred from this pattern," Umstadter says.

As multiples of the laser-light frequency, the harmonics represent higher energies. Even more energetic harmonics in the X-ray range may be possible. The Michigan researchers are planning new experiments to reach those frequencies.

Toshiki Tajima of Lawrence Livermore (Calif.) National Laboratory agrees that the recent experiment buoys hopes for "a new way to generate bright X rays in a very compact and, perhaps, very cheap way." Umstadter says the new results also have implications for laser-driven nuclear fusion and laboratory tests of astrophysical phenomena.

Eric J. Prebys of Princeton University says that the new work confirms earlier experiments that also demonstrated that electrons can be propelled to near-light speeds by laser electric fields. Umstadter, however, claims that his group is the first to see unequivocally the instantaneous magnetic effect.
COPYRIGHT 1998 Science Service, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1998, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:compact lasers offer potential advances in accelerators
Author:Weiss, P.
Publication:Science News
Article Type:Brief Article
Geographic Code:1U3MI
Date:Dec 19, 1998
Words:440
Previous Article:Ancient ancestor reveals skeletal stamina.
Next Article:Sleeping birds might be proofing songs.
Topics:


Related Articles
Is the force with lasers? Will lasers be selected for the Strategic Defense Initiative?
Bright prospects for laboratory lasers.
Cascades of light shine from a new laser.
Drawing a bead on quantum dot lasers.
Electrons hang-ten on laser-made waves.
Pushy lasers sweep into ion race.
Ring around the proton.
Hot flashes, cold cuts: ultrafast lasers give power tools a new edge.
Light rambles through room-temperature ruby. (Physics).
Laser landmark: silicon device spans technology gap.

Terms of use | Privacy policy | Copyright © 2021 Farlex, Inc. | Feedback | For webmasters