Linac Coherent Light Source (LCLS)

The Linac Coherent Light Source Undulator Hall.

The LCLS is the world’s first hard x-ray free electron laser facility capable of producing x-rays that are both very intense and clumped into ultrafast pulses.
Menlo Park, California Location
2010 Start of Operations
869 (FY 2022) Number of Users


The LCLS, at the SLAC National Accelerator Laboratory, is the world’s first hard x-ray free electron laser facility and became operational in June 2010. This is a milestone for x-ray user facilities that advances the state-of-the-art from storage-ring-based third generation synchrotron light sources to a Linac-based light source. The LCLS provides laser-like radiation in the x-ray region of the spectrum that is 10 billion times greater in peak power and peak brightness than any existing coherent x-ray light source. The SLAC linac provides high-current, low-emittance 5 – 15 GeV electron bunches at a 120 Hz repetition rate. A newly constructed long undulator bunches the electrons, leading to self-amplification of the emitted x-ray radiation, constituting the x-ray FEL.


Unlike conventional lasers, the LCLS is a free-electron laser (FEL), creating light using high energy electrons travelling in a vacuum through undulator magnets that steer the electrons back and forth. The electrons are produced and accelerated using the final third of SLAC’s two-mile linear accelerator. With its ultra-bright, ultrafast (femtosecond scale) pulses, the LCLS allows scientists to capture images of atoms and molecules in action with femtosecond time resolution. It provides scientists with a unique tool for studying the arrangement and motion of atoms, and electrons in metals, semiconductors, ceramics, polymers, catalysts, plastics and biological molecules with the potential to significantly impact the advancement of energy research and other scientific research fields.