The world's brightest X-ray machine has come to life at the SLAC National Accelerator Laboratory in the hills near Stanford University. The mile-long machine produces a laser beam made of X-rays instead of visible light. Its laser bursts are so bright and so brief that researchers will use them as an ultrafast camera to capture the details of things previously unseen, such as the arrangement of atoms in metals, semiconductors, ceramics, polymers and proteins. "So you can look at a process like photosynthesis one molecule, one step at a time," said SLAC Director Persis Drell. The laser is expected to have wide-ranging impacts on medicine, advanced energy research and other fields.

The $420 million Linac Coherent Light Source (LCLS) is now the main ingredient on the scientific menu at SLAC. After four decades of using the lab's 2-mile-long linear accelerator to produce high-energy electrons for cutting-edge physics experiments, researchers have turned their attention to using the famous accelerator to create the X-ray laser. The extremely short wavelengths of the LCLS give the laser the ability to take freeze-frame snapshots down to the atomic level.

The LCLS creates its laser by accelerating a beam of electrons through a series of magnets in a room known as the Undulator Hall. The alternating magnetic field created by the magnets causes the electron beam to wiggle from side to side as it passes by. As the electrons change course, some of their energy is converted to X-rays, which are organized into a coherent laser beam.

The laser will be a game-changer for scientists who want to study chemical reactions at their most basic. Until now, watching atoms as they formed or broke molecular bonds was essentially observing a blur. "You can see the beginning state, you can see the end state, and then something happens in the middle and it's a blur," Galayda said. But the high resolution provided by the X-ray laser will allow researchers to compile a series of snapshots of molecules as they change shape during reactions, and then string those images together to create a never-seen-before movie.

SLAC is operated by StanfordUniversity for the U.S. Department of Energy. The LCLS project is collaboration among several DOE National Laboratories, including SLAC, Argonne, Lawrence Berkeley and Lawrence Livermore National Laboratories; and CornellUniversity and the University of California-Los Angeles. Pacific Northwest National Laboratory provided additional project management.

By Vasil Sidorov on April 22, 2009 after Stanford Report

E-mail: sidorovvasil@gmail.com