collage of LCLS-II milestones
LCLS-II news collection

Building the world’s most powerful X-ray laser

An upgrade to SLAC’s renowned Linac Coherent Light Source will allow it to deliver X-ray laser beams that are 10,000 times brighter with pulses that arrive up to a million times per second.

Hundreds of scientists use LCLS each year to catch a glimpse of nature’s fundamental processes. The unique X-ray microscope uses some of the brightest, fastest X-ray pulses ever made to provide unprecedented details of the atomic world.

LCLS-II will allow researchers to make observations over a wider energy range, capture detailed snapshots of rapid processes, probe delicate samples and gather more data in less time. Powered by a superconducting accelerator, LCLS-II will further sharpen our view of how nature works at the atomic scale and help advance transformative technologies of the future, including novel electronics, life-saving drugs and innovative energy solutions.


LCLS-II: The next leap for X-ray science

Latest LCLS-II news

News feature

The Secretary celebrated LCLS-II first light with 600 SLAC staff and collaborators Oct. 26.

Secretary of Energy Jennifer M. Granholm and SLAC staff celebrate LCLS-II first light

With up to a million X-ray flashes per second, 8,000 times more than its predecessor, it transforms the ability of scientists to explore atomic-scale, ultrafast phenomena that are key to a broad range of applications, from quantum materials to clean...

LCLS-II first light

The facility is now one step away from releasing an unprecedented stream of ultra-bright X-rays.

This is a graphic representation of electron bunches travelling through SLAC's linear accelerator.

En route to record-breaking X-rays, SLAC’s Cryogenic team built a helium-refrigeration plant that lowers the LCLS-II accelerator to superconducting temperatures.

Images of frost and a thermometer superimposed over an aerial view of an accelerator building.

The facility, LCLS-II, will soon sharpen our view of how nature works on ultrasmall, ultrafast scales, impacting everything from quantum devices to clean energy.

LCLS-II cooldown

Over the past few years, Kathleen Ratcliffe and Tien Fak Tan have worked together to help build the superconducting accelerator that will drive new scientific discoveries at SLAC’s X-ray laser.

SLAC's Tien Tan, left, and Kathleen Ratcliffe pose for a portrait outside a SLAC building.

When upgrades to the X-ray laser at the Department of Energy’s SLAC National Accelerator Laboratory are complete, the powerful new machine will capture up to 1 terabyte of data per second; that’s a data rate equivalent to streaming about one...

Infographic on LCLS-II data.
Media mentions

LCLS-II in the news

Media contact

Manuel Gnida
Media Relations Manager

LCLS-II explained

The upgrade to the Linac Coherent Light Source, LCLS-II, will be a transformative tool for energy science, qualitatively changing the way that X-ray imaging, scattering and spectroscopy can be used to study how natural and artificial systems function. It will produce X-ray pulses that are 10,000 times brighter, on average, than those of LCLS and that arrive up to a million times per second. Learn what an XFEL does and about SLAC’s journey to upgrading its Linac Coherent Light Source.

X-ray free-electron lasers are like X-ray microscopes, allowing scientists to spot the intricate movements of atoms and molecules and capture their motion in snapshots that can be strung together into “molecular movies” of materials, chemistry and biology in action.

Molecular movie filmstrip.

SLAC’s renowned Linac Coherent Light Source is getting a major upgrade that will significantly boost its power and capacity. LCLS-II will further sharpen our view of how nature works at the atomic scale and help advance transformative technologies of the future, including novel electronics, life-saving drugs and innovative energy solutions.

Aerial view of linac and cryoplant at SLAC

At the heart of LCLS-II is a superconducting accelerator made up of 37 cryomodules with strings of super-cold niobium cavities. Linked together and chilled to nearly absolute zero, they will accelerate electrons to almost the speed of light and power an upgrade to the nation’s only X-ray free-electron laser facility.

A worker unveiling a cryomodule on a truck.

LCLS was designed to generate X-ray pulses a billion times brighter than anything that had come before. It was the first machine to produce ultrafast high energy X-ray laser pulses. Since it turned on in April 2009, SLAC has been the birthplace of a host of scientific firsts. LCLS-II will bump X-ray science to new heights.

Undulator Hall
Image Gallery

Building a next-gen X-ray laser

Building a Next-Gen X-ray Laser
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Photo collage of LCSL social media posts


LCLS-II was developed and built in collaboration with four other DOE national laboratories: ArgonneBerkeley LabFermilabJefferson Lab, and Cornell University.

  • Argonne National Laboratory
  • Berkeley Lab
  • Fermilab
  • Jefferson Lab
  • Cornell University

International partners

  • DESY
  • European XFEL
  • CEA Saclay
  • CERN



For questions or comments, contact the SLAC Office of Communications at

SLAC is a vibrant multiprogram laboratory that explores how the universe works at the biggest, smallest and fastest scales and invents powerful tools used by scientists around the globe. With research spanning particle physics, astrophysics and cosmology, materials, chemistry, bio- and energy sciences and scientific computing, we help solve real-world problems and advance the interests of the nation.

SLAC is operated by Stanford University for the U.S. Department of Energy’s Office of Science. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time.