Brittany Nelson-Cheeseman at ALS Beamline 4.0.2 - Magnetic and Biochemical Spectroscopy. 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. 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.