Argonne helps build new bright light source |
|
In combination with five other laboratories, Argonne is helping to build the Linac Coherent Light Source (LCLS), which will produce X-ray light with a peak brightness more than 100 billion times that of current synchrotron light sources, such as the Advanced Photon Source (APS), making the LCLS the most brilliant X-ray source in the world. Argonne is working with Stanford Linear Accelerator Center (SLAC), Brookhaven National Laboratory, Los Alamos National Laboratory, Lawrence Livermore National Laboratory, and the UCLA Particle Beam Physics Laboratory on the roughly $220 million DOE-supported LCLS project under way at SLAC in Menlo Park, Calif. Argonne will be in charge of building the $50 million subway-train-length undulator system at the end of the SLAC linear accelerator. The undulator, a critical component of the LCLS, is a high-precision magnet system used to undulate, or oscillate, electrons causing them to radiate waves of X-ray light. In addition, Argonne will build the vacuum system, power supplies, diagnostics and everything else needed for the undulator system. Building the
largest undulator system “Researchers are taking an approach that will emit X-ray pulses less than 200 femtoseconds, 1,000 times shorter than those in use at APS today,” said Murray Gibson, associate laboratory director for the APS, of this fourth-generation synchrotron light source. A femtosecond is a trillionth of a second. Research that can be conducted using the LCLS ranges from biological to materials science. The extremely high LCLS peak brightness and ultrashort pulse lengths may be used to observe the motion of nanoscale structures, to hollow out an atom or to measure inter-atomic distances in a molecule that is undergoing a chemical reaction. With such extreme properties, the LCLS might even be able to image a single molecule. By understanding the resulting scattering of the light and by using different exposures to determine the molecule’s orientation, the molecular structure could be determined, eliminating the need for protein crystallography. “The LCLS shows promise in doing just that, and it will allow us to really extend the capability of what is already being done in the study of large biomolecules,” Milton said. Electron coaxing “If one were able to do a trick with particles and make all of the electrons in a single bunch radiate their light at exactly the same phase, then the light would add up in a more favorable way than it does out in the APS,” said Milton, “and this is basically what happens in the LCLS.” APS researchers, including Milton, were the first to demonstrate this process, known as self-amplified spontaneous emissions, at visible and ultraviolet wavelengths. The LCLS approach is not ideal for every X-ray experiment. For example, its intense X-ray light might destroy the material being studied. “While some experiments can take place at the LCLS, it is not a user facility but a test facility to determine what is possible and what will be demanded,” said Gibson. “We know that the LCLS will work, but we need to optimize its uses.” The SLAC LCLS is expected to perform first tests in 2007 and begin operation in 2009. After gaining some experience with the experimental facility, a fourth-generation X-ray laser may be built in the United States within the next 20 years. Even then, its specialized laser-like X-ray radiation means it will be a unique complement to established light sources, such as the APS. For more information, please contact Catherine Foster. |