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An Office of Science User Facility

About LCLS

LCLS takes X-ray snapshots of atoms and molecules at work, revealing fundamental processes in materials, technology and living things. Its snapshots can be strung together into movies that show chemical reactions as they happen.

Approximately 600 scientists each year conduct groundbreaking experiments into the fundamental processes of chemistry, materials and energy science, biology and technology at LCLS. Its experiments generated about 500 articles in peer-reviewed scientific publications in the first five years of operation, with almost a quarter of them appearing in prominent journals like Science and Nature.​

New Extremes for X-ray Science

Image - This illustration depicts an experiment at SLAC that revealed how a protein from photosynthetic bacteria changes shape in response to light.  

LCLS creates X-ray pulses a billion times brighter than previously available at synchrotrons.

Pulses are fired about 120 pulses per second, each one lasting just quadrillionths of a second, or "femtoseconds" -- a timescale at which the motion of atoms can be seen and tracked. The pulses allow scientists to study important proteins at room temperature, in some cases even while they are active.

Already, LCLS has enabled scientists to uncover the 3-D molecular structure of an enzyme involved in the transmission of African sleeping sickness, to study how a new type of painkiller with potentially reduced side effects interacts with a specialized protein that regulates the body’s pain response, to obtain live snapshots of steps during the water-splitting reaction in photosynthesis, and to study the microscopic components of air pollution at the nanoscale.

Scientists have been able to measure shock waves in metals heated to millions of degrees. At the other extreme, LCLS has provided a first glimpse of the structure of supercooled water, which remains liquid well below its normal freezing temperature, and opened a new window into tiny quantum tornadoes, which form in fast-spinning droplets of supercooled liquid helium.

A Broad Reach

Image - diffraction pattern of Trypanosoma brucei cathepsin B protein  

LCLS is enabling pioneering research across many fields:

Harnessing the sun’s light: Photosynthesis is one of the most important chemical reactions on Earth, yet most aspects are not fundamentally understood. With LCLS, researchers can directly observe the natural processes that convert the sun’s light into usable energy, with promising implications for America’s energy future.

Aiding drug development: Scientists are using LCLS to determine the structures of proteins from tiny nanocrystals. This unique capability opens the door to studying tens of thousands of biological structures that were out of reach before, including proteins important in disease and its treatment. LCLS has enabled detailed structural studies of membrane proteins, which are key targets for drug discovery; its unique pulses offer important advantages over more conventional X-ray sources in advancing membrane protein research.

Developing future electronics: Experiments at LCLS are exploring new ways to design and control the magnetic and electronic properties of electronic materials with ultrashort pulses of light. This could ultimately lead to extremely fast, low-energy computer memory chips and data-switching devices.​​​​

Designing new materials and exploring fusion: LCLS gives scientists the right tools to investigate, as never before possible, the extremely hot, dense matter at the centers of stars and giant planets. These experiments help researchers explore how materials respond to stress, design new materials with enhanced properties, and attempt to replicate the nuclear fusion process that powers the sun.

Customizing chemical reactions: Research at LCLS is improving our understanding of the earliest steps in chemical reactions, including catalytic reactions that are critical in producing fuels and other industrial chemicals. This improved understanding of ultrafast chemistry at the scale of atoms and molecules could lead to more efficient and controllable chemical reactions.

How It Works

Image - In this illustration of a severed methyl iodide molecule, electrons jump the gap from one fragment containing carbon and hydrogen atoms (right) to the other fragment, which contains an iodine atom (left). 

LCLS was the first laser in the world, and one of just two now in operation, to produce "hard," or very-high-energy X-rays. The process of producing X-ray pulses starts in a section of SLAC's linear accelerator.

First a drive laser generates a precise pulse of ultraviolet light, which travels to an injector "gun" and strikes the surface of a copper plate. The plate responds by releasing a burst of electrons, which are accelerated by a series of devices to boost their energy.

The electron pulses then enter the LCLS Undulator Hall, the heart of LCLS, where they are put to work generating X-ray laser light.

The Undulator Hall houses thousands of special magnets, spaced a few millimeters apart and arrayed so their north-south magnetic poles alternate. The poles alternately attract and repel passing electron bunches, which swerve back and forth in an undulating motion that forces them to give off X-rays.

As each electron bunch travels with its associated X-rays, they start to interact with each other. The electrons arrange themselves in parallel sheets; this causes the waves of X-ray light to line up so their crests and troughs match, creating “coherent” or laser light and greatly boosting the power of the X-ray pulses. At this point the electrons are no longer needed; they are safely discarded, and the X-ray laser pulses continue in a straight line to LCLS experiments, arriving at a rate of up to 120 pulses per second.

X-rays are delivered to any of six specialized experimental stations, and in some cases to multiple stations simultaneously. Each station has a dedicated team of scientists and support staff who spearhead R&D efforts, engage in innovative research and assist users with experiments.

Each station is equipped with a suite of instruments that use specialized techniques to gather data, from telltale signatures of electrons and ions to the intricate patterns left by crystallized samples struck by the X-ray laser. Work has begun on a seventh experimental station that will focus on solving the 3-D structures of hard-to-study proteins and other biological samples.

Infographic showing ultrafast, ultrasmall scales  

What's Next

The scientific advancements at LCLS have garnered worldwide attention, and work has begun on a revolutionary new tool, LCLS-II. The new capabilities provided by LCLS-II’s increased repetition rate and energy range will allow scientists to study how light triggers chemical reactions in gases and physical changes in materials. They will also allow study of the high-resolution structure of matter under extreme conditions, such as high pressures and high temperatures.

With LCLS-II, SLAC will continue to advance the frontiers of X-ray research, keeping the United States at the forefront of this very competitive international arena and supporting transformational science for the coming decade.

In addition to delivering the upgraded facility, SLAC will continue to pursue an integrated and focused R&D program to maximize the scientific impact of LCLS-II and to prepare for future facilities.​​​​​​​​​​​​


 A Long History of Imaging Breakthroughs

​​The LCLS photographs atomic motion much as a “strobe” flash is used to photograph the motion of a bullet in flight. This latest advance in stop-action imaging at Stanford has roots going back more than 100 years. 

Around 1872, Eadweard Muybridge started making stop-motion photographs of people, animals, and trains in motion on Leland Stanford’s farm. He is famous for showing that all four of a horse’s feet leave the ground during a gallop. 

To be able to click a shutter fast enough to show each stride a horse makes when galloping required tremendous engineering ingenuity. The LCLS provides X-rays of such shortness and precision that stroboscopic experiments can be done with materials on the nanoscale, and even with individual molecules and atoms.

Comparison of a series of images of a horse in motion with a series of images of a molecule in motion. 


 How Fast Is a Femtosecond?

2.4 seconds: The time it takes light to travel the distance to the moon and back—about 480,000 miles.

100 femtoseconds: the time it takes light to travel the width of a human hair.


 Modern X-ray Science


One of the most active areas of X-ray light-source research is protein crystallography. To determine the structure of a protein, scientists obtain a crystalized sample of protein molecules where all the atoms are ordered into a regular pattern. The crystal sample is usually no bigger than a grain of salt.

Protein molecule 

Exposing the crystal to a beam of intense, highly focused X-rays creates a unique pattern of dots on a detector. The spots—called Laue spots—are used to calculate the locations of atoms within the protein molecules.

This technique earned Stanford’s Roger Kornberg the 2006 Nobel Prize in chemistry. Kornberg and colleagues used protein crystallography to solve the structure of RNA polymerase, which contains over 30,000 individual atoms. RNA polymerase plays a key role in how information stored in DNA is translated into the proteins of life.

The LCLS is revolutionizing protein crystallography by making “single-shot” images of molecules that resist forming crystals.

SLAC SLAC National Accelerator Laboratory, Menlo Park, CA
Operated by Stanford University for the U.S. Dept. of Energy