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CONTACT: Neil Calder, SLAC: (650) 926-8707,

COMMENT: John Galayda, SLAC: (650) 926-2371,

Funding is approved for next-generation light source

Just as the Hubble telescope vastly increased our ability to see "out," the Linac Coherent Light Source (LCLS) project at the Stanford Linear Accelerator Center (SLAC) will vastly increase our ability to see "in."

The LCLS project passed the Department of Energy's Critical Decision 1 process in October 2002, and $6 million is allocated in President Bush's budget for FY03 for the start of engineering design activities.

The LCLS project is a proposed multi-institutional collaboration for an X-ray free electron laser (X-FEL) using electron beams from the SLAC linear accelerator (linac) and operating in the wavelength region of 1.5-15 (0.15-1.5 billionths of a meter). The institutions with major LCLS responsibilities include SLAC, Argonne National Laboratory, Lawrence Livermore National Laboratory and UCLA. The Los Alamos National Laboratory and Brookhaven National Laboratory also are collaborators on the project.

"Each generation of synchrotron light sources has had tremendous impact on the physical and life sciences," said SLAC researcher and LCLS Project Director John Galayda. "These light sources are very powerful research tools for determining the locations and properties of atoms in molecules, solids and liquids. The LCLS will produce flashes of X-rays 10 billion times brighter and 1,000 times shorter [in duration] than any existing source. These pulses will be used like a strobe flash to watch atoms as they form or break bonds inside molecules or leave the surface of a solid."  

Vast improvement

The LCLS will have properties vastly exceeding those of all current X-ray sources in three key areas. The peak brightness of the LCLS will be 10 orders of magnitude greater than current synchrotrons. The light will have full spatial coherence and enhanced temporal coherence and be "laser-like," enabling many new types of experiments. And, at 230 quadrillionths of a second, the pulses will be ultra-short, enabling studies of fast chemical and physical processes. These characteristics will open new realms of scientific applications in the chemical, materials and biological sciences.

The LCLS also will be used to bring about changes in materials by flash-heating solids or gases to produce plasmas and excited atoms in states impossible to create or observe before. The LCLS will be so bright, researchers will be able to determine the structure of individual large molecules without requiring that millions of copies be ordered in a crystal lattice hence "crystallography without crystals." Such advances have broad implications for understanding structure and dynamics in nanostructured materials.

In the LCLS, the X-FEL will receive a beam of electrons accelerated through the last third of the 2-mile (3-kilometer) SLAC linac. The electron beam will make a single pass through a 122-meter array of magnets called an undulator. The undulator will force the beam of electrons to move from side-to-side. Forcing the electrons to wiggle from side-to-side will cause them to emit X-ray photons photons having much higher energies and much shorter wavelengths than the photons that we perceive as visible light. When the magnetic field of the undulator, the electron beam and the photons are tuned into exquisite harmony with one another, the electric field of the X-ray photons will "herd" the electrons in much shorter bunches than have been achieved before. The short electron bunches will produce radiation as if each bunch were a single electron with a tremendous electric charge. The bunches will be spaced so the X-ray waves they emit are matched up, crest-to-crest, in near-perfect unison. These electron bunches will generate a laser-like X-ray beam 10 billion times brighter than the light currently produced in the synchrotron at the Stanford Synchrotron Radiation Laboratory.

The LCLS project builds on the capabilities of the existing SLAC linear accelerator and relies on the vast body of experience of SLAC's operators and researchers. LCLS also capitalizes on the fact that the particle collider research and development team has produced a long series of successful results in the generation and control of electron beams.

The estimated design and construction cost for the LCLS project is about $220 million. SLAC's proposed construction schedule calls for first attempts to produce X-ray laser light by the end of 2007 and full operation by September 2008.


By Tom Meed

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