Advanced Light Source

The Advanced Light Source (ALS) is a research facility at Lawrence Berkeley National Laboratory in Berkeley, California. One of the world's brightest sources of ultraviolet and soft x-ray light, the ALS is the first "third-generation" synchrotron light source in its energy range, providing multiple extremely bright sources of intense and coherent short-wavelength light for use in scientific experiments by researchers from around the world. It is funded by the US Department of Energy (DOE) and operated by the University of California. The current ALS director is Roger Falcone.

The ALS serves about 2,000 researchers ("users") every year from academic, industrial, and government laboratories worldwide. Experiments at the ALS are performed at nearly 40 beamlines that can operate simultaneously over 5000 hours per year, resulting in about 600 scientific publications annually in a wide variety of fields. Any qualified researcher can propose to use an ALS beamline. Peer review is used to select from among the most important proposals received from researchers who apply for beam time at the ALS. No charge is made for beam time if a user's research is nonproprietary (i.e., the user plans to publish the results in the open literature). About 16% of users come from outside the US.

Electron bunches traveling near the speed of light are forced into a nearly circular path by magnets in the ALS storage ring. Between these magnets there are straight sections where the electrons are forced into a slalom-like path by dozens of magnets of alternating polarity in devices called "undulators." Electrons emit beams of electromagnetic radiation—from the infrared through the visible, ultraviolet, and x-ray regimes—under the influence of these magnets. The resulting beams, collimated along the direction of the electrons' path, shine down beamlines to instruments at experiment endstations.

Lower-energy soft x-ray light is the ALS specialty, filling an important niche and complementing other DOE light source facilities. Higher-energy x-rays are also available from locations where superconducting magnets create "superbends" in the electrons' path. Soft x-rays are used to characterize the electronic structure of matter and to reveal microscopic structures with elemental and chemical specificity. Research in materials science, biology, chemistry, physics, and the environmental sciences make use of these capabilities.

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