Physicists at Argonne National Laboratory have now bested a world record, coaxing the most energetic beam of light yet from a mirrorless free-electron laser. Although the laser fell short of delivering x-raysthe ultimate goal of this kind of synchrotron radiation researchthe beam produced in the experiment was 1,000 times more energetic than previous attempts, having a wavelength of 385 nanometers. "In the history of synchrotron radiation research, which is only about 45 years old, you can count the true breakthroughs on the fingers of one hand," says David Moncton, Argonne's Associate Laboratory Director for the Advanced Photon Source. "This is one of them. Our team received congratulatory e-mails from dozens of colleagues all over the world who are working on this same problem."

Scientists hope that free-electron lasers will become the next-generation x-ray source for a range of research problemsfrom probing the structure of single proteins to studying so-called warm, dense matter. Unlike conventional lasers, which use mirrors to amplify the light they create, free-electron lasers rely on a high-quality electron beam and an array of magnets. The magnets jostle the electrons until they emit light pulses. The longer the magnet array, the higher the electron energy and the higher the light energy. Six U.S. research organizations are collaborating to develop the device, which they say could in theory generate an x-ray beam with a peak brightness one billion times greater than the brightest beam currently available.