LCLS Overview

LCLS Overview

LCLS takes X-ray snapshots of atoms and molecules at work, providing atomic resolution detail on ultrafast timescales to reveal fundamental processes in materials, technology and living things. Its snapshots can be strung together into “molecular movies” that show chemical reactions as they happen.

With over 13,000 scientific user visits in its first 10 years of operation, researchers from around the world have conducted groundbreaking experiments in fields as diverse as chemical catalysis, human health, quantum materials science, and the physics of planetary formation. Data from LCLS experiments have generated over 1450 articles in peer-reviewed scientific publications, with a quarter of them appearing in prominent journals like Science and Nature.​

Since the start of operations in 2009:

3,000+ Unique users
900+ Experiments
1450+ Publications

New Extremes for X-ray Science

LCLS currently delivers 120 X-ray 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.

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

Over the past few years, LCLS has enabled scientists to uncover the 3-D molecular structure of proteins involved in the transmission of many important diseases, such as African sleeping sickness, Dengue fever and the Zika virus; it has aided the development of next-generation painkillers that seek to reduce side effects such as drug dependency; it has obtained live snapshots of the fleeting steps in the water-splitting reaction in photosynthesis; and it has studied the microscopic components of air pollution at the nanoscale.

Scientists have been able to measure stress, strain and failure in advanced aerospace materials, and have studied how matter behaves under the extreme pressures that drive the formation of planets. At another 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

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.

Protein Structure

Revealing Life's Secrets & 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.

Future Electronics

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.

Matter in Extreme Condition Research

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

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

LCLS Aerial

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.

LCLS Undulator Hall

LCLS Transport Hall

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 seven 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.

What's Next

LCLS-II Aerial

A major upgrade to the facility, known as LCLS-II, is underway. This will provide a revolutionary leap in capability by increasing the X-ray pulse repetition rate from 120 pulses per second to 1 million pulses per second!

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 enable new ways to capture rare chemical events, study quantum materials with unprecedented resolution, and track the behavior of fluctuation biological systems.

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.

Further Exploration

Ultrafast X-ray Science

Ultrafast X-Ray Science: Groundbreaking Laser Takes Discovery to New Extremes →

The world at the atomic scale is never at rest, with particles moving so quickly and molecular bonds changing so rapidly that we have been unable to capture their motion directly until now.


SLAC knows how the universe works. Now it's targeting your needs →

A particle accelerator's $1 billion upgrade could lead to improvements in electronic gear. Also in SLAC's sights: better batteries and cancer treatments.

Femtosecond Science at SLAC

Femtosecond Science at SLAC →

Explore femtosecond science at SLAC through interactive infographic, videos, Q & A with scientists, virtual tours of LCLS, etc.

What is a molecular movie?

What is a molecular movie? →

Molecular movie-making is both an art and a science; the results let us watch how nature works on the smallest scales.