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The SLAC National Accelerator Laboratory, in Menlo Park, California, has a 3-kilometre-long electron accelerator. Credit: Matt Beardsley/SLAC National Accelerator Laboratory
An X-ray laser, upgraded to become the most powerful in the world, produced its first beams on 12 September. Located in Menlo Park, California, the laser will produce one million X-ray pulses per second when running at full capacity. Scientists are excited to get a crack at the instrument, called LCLS-II, which will make it possible to create high-speed movies of ultrafast processes, including electrical charges hopping around atoms during a chemical reaction. Such studies could unlock the secrets of photosynthesis and aid in the development of new electronic materials for computing systems.
Europe’s X-ray laser fires up
Europe’s X-ray laser fires up
The US$1.1-billion upgrade to the Linac Coherent Light Source (LCLS), housed at the SLAC National Accelerator Laboratory, has been in the works for more than a decade. It has increased the instrument’s repetition rate — how many pulses fire in a set time — roughly 8,000-fold, and the laser’s brightness by, on average, 10,000-fold. These changes will enable chemists and biologists to make molecular movies with a crispness never seen before, and will offer a look inside rare molecular events invisible to other instruments.
“We are waiting for the LCLS-II so we can do our dream experiment that we’ve been preparing for ten years,” says Junko Yano, a molecular biophysicist at Lawrence Berkeley National Laboratory in Berkeley, California.
The facility “opens up entirely new possibilities” for various types of research, including quantum materials science, says Mike Dunne, director for the LCLS.
The original LCLS, now called LCLS-I, started up in 2009, becoming the first instrument in the world to combine the atom-probing capabilities of high-energy ‘hard’ X-rays with the speed of a laser. The instrument had a 3-kilometre-long particle accelerator that sent electrons zipping through a copper pipe. The electrons were then pumped into one of two sets of magnetic undulators, which caused the electron beam to wiggle from side to side and emit X-rays. One set produced ‘hard’ X-rays, and the other made lower-energy ‘soft’ X-rays. When SLAC, which is run by Stanford University in California and funded by the US Department of Energy, built LCLS-I, scientists weren’t totally sure it would work, Dunne says. “It was a leap into the unknown.”
But it was a success. Other countries followed suit: similar systems were built in South Korea, Japan, Switzerland and Germany. It was a revolution to do “ultrafast science with atomic resolution”, says Sakura Pascarelli, scientific director of the European X-ray Free-Electron Laser (XFEL) near Hamburg, Germany, which opened to users in 2017.
The undulator system that creates LCLS-II’s X-rays has been upgraded over the past decade. Credit: Alberto Gamazo/SLAC National Accelerator Laboratory
The upgrade to LCLS-I replaced part of the copper pipe on the electron accelerator with cryogenically cooled niobium cavities. These are superconducting when brought to temperatures around 2 kelvin, so they can conduct electrons continuously with nearly zero resistance. This helps LCLS-II to achieve its faster X-ray pulse rate. At the moment, the supercooled part of the instrument is making only soft X-rays.
LCLS-II was originally scheduled to fire up in 2020, but various factors, including the COVID-19 pandemic, revised that timetable, Dunne says. “This is completely new technology,” he adds. Even working out how to transport the superconducting cavities across the country from Illinois, where they were built, took time.
Chemists and biologists have watched the upgrades with anticipation. Yano used LCLS-I, as well as an X-ray free-electron laser in Japan to reveal how, at the atomic level, a protein complex called photosystem II splits water and produces oxygen during photosynthesis. She and her collaborators homed in on a key cluster of metal atoms in the complex and tracked its structure as it moved through four energy states before releasing oxygen. They described their results in Nature this year1.
But Yano wants to go further. “Knowing the structure is one thing,” she says. “We also want to know how charges around the metal are distributed”, as well as how the ‘spins’ of the electrons hopping around the complex change. This will help the team to understand how photosynthesis occurs, and could help researchers looking to mimic the incredible efficiency of the process in solar-fuel production systems, for instance. That experiment requires extraordinarily rapid pulses of soft X-rays, Yano says, so LCLS-II is the only facility at which it can be done. Her team has submitted a proposal asking for time to use the instrument.
X-ray science: The big guns
X-ray science: The big guns
Dunne says that the X-ray pulses at LCLS-II are also exciting because their sheer power will enable scientists to work with more dilute samples of chemicals and biomolecules. That should spare a graduate student studying photochemistry a few years of work synthesizing enough of a new molecule to study it. And it will allow chemists to study promising catalysts — which are used, often in trace amounts, to speed up reactions — under more realistic conditions.
The SLAC team is already planning the next series of upgrades, to bring the hard X-ray beam up to a megahertz pulse rate. At the moment, the European XFEL is the fastest source of hard X-rays, generating 27,000 pulses per second. Another X-ray laser being built in Shanghai, China, might offer competition when it starts up, no earlier than 2025: it aims to generate one million X-ray pulses per second, too.
“I’m sure we’ll be leapfrogged,” Dunne says. Generally, one facility holds the record for a while, until another is upgraded and becomes more powerful, Pascarelli says. “We’re pushing each other.”
For now, the SLAC team is celebrating years of work, and evaluating proposals from scientists around the world asking to use LCLS-II to advance their research.
doi: https://doi.org/10.1038/d41586-023-02874-1
Bhowmick, A. et al.Nature 617, 629–636 (2023).
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Professor Faculty Position - Medical Imaging
Duke University Pratt School of Engineering
Baylor College of Medicine (BCM)
We seek tenure-track faculty candidates at the level of Assistant Professor with interests in microbial genetics, microbial physiology
Lyda Hill Department of Bioinformatics
At the Faculty of Medicine of Rheinische Friedrich-Wilhelms-Universität Bonn, the Clinic for Internal Medicine III (Oncology, Hematology and Rheuma...
Bonn University Hospital (AöR)
You have full access to this article via your institution.
Europe’s X-ray laser fires up
X-ray science: The big guns
Particle physicists want to build the world’s first muon collider
How the revamped Large Hadron Collider will hunt for new physics
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