LLE's Omega boosts laser-driven fusion

esearchers at the Laboratory for Laser Energetics have successfully completed the first full-scale test of a technique to improve laser-driven fusion. Implosions using this technique, called polarization smoothing, generate 70 percent more fusion neutrons than without and move researchers closer to self-sustaining fusion.

LLE houses the world's most powerful laser: the 60-beam Omega. Omega is often used as a testing ground for technologies that are planned for the National Ignition Facility under construction in California. Since the process shows such promise, it will be incorporated into each of the NIF's 192 laser beams for direct-drive implosions.

Omega fires its energy on a millimeter-sized pellet, causing the pellet to implode, crushing in on itself and triggering nuclear fusion. Initiating this implosion with 60 beams, however, is like trying to crush a balloon between two hands: Though force is exerted with the fingers, the balloon bulges out between them. Likewise, if the energy from each beam of the laser pushes harder in one spot than another, the pellet will implode unevenly, losing some potential to trigger fusion.

To combat this uneven pressure, scientists have developed ways of "smoothing" the beams so they strike the pellet evenly. Imagine the shadow rings a flashlight shines on a wall, smoothing out to a perfectly even circle of light. The more smoothing, the more wallop the laser can throw at the target. Scientists looked to polarization--the tendency of light waves to vibrate in only one plane--to find a way to smooth the beams even more.

"The idea of polarization smoothing has been around for some time, but this is the first time it's been used on a laser of this scale," said scientist David Meyerhofer, professor of mechanical engineering.

Maintained by University Public Relations
Please send your comments and suggestions to:
Public Relations.