World’s most powerful X-ray free electron laser soon online

The device's applications are many including uses in clean energy and pharmaceuticals.
Loukia Papadopoulos
Crews install a cryomodule at SLAC.

The US Department of Energy’s SLAC National Accelerator Laboratory is preparing to power the world’s most powerful X-ray free electron laser by getting electrons to fly through a new superconducting accelerator. Called the Linac Coherent Light Source II (LCLS-II), the new project is almost ready to release an unprecedented never-before-witnessed stream of ultra-bright X-rays.

This is according to a press release by the laboratory published on Monday.

“Seeing electrons make it all the way through the LCLS-II is proof that our idea to make the source for an extremely powerful superconducting X-ray machine at SLAC is going to work,”said in the statement Dan Gonnella, lead scientist at SLAC and a group leader in the accelerator directorate.

“We were confident in our work, but until you see the first electrons actually make it through, you are feeling the butterflies.”

A decade of work

The lofty endeavor took more than a decade of work and saw the collaboration of four national laboratories: Argonne, Berkeley Lab, Fermilab, and Jefferson Lab. Cornell University also contributed to the research.

The end result is nothing short of impressive.

“LCLS-II will produce X-rays that are 10,000 times brighter than those of SLACs existing free-electron laser facility, LCLS – a historic upgrade that will open previously unimaginable views into some of the most pressing scientific questions of our time. The facility will release one million X-ray flashes per second, far more than LCLS’s current rate of 120 flashes per second,” noted David Krause in the press release.

The applications to come out of the experiment are many and varied including “harvesting solar energy for a new generation of clean fuels, inventing sustainable manufacturing methods for industry, and designing a new generation of drugs based on the ability to create molecular movies of how our bodies respond to disease.”

This has got the engineers at SLAC excited!

“We are not answering only a few questions with the new superconducting accelerator, we are letting scientists answer an incredible number of questions,” SLAC electronics engineering manager Andy Benwell said.

Free of dust

Achieving this milestone however did not come easily. For 10 years, the team worked hard to keep the new facility pristine and free of dust as it can swiftly destroy the performance of the superconducting cavities. 

“There were certainly opportunities for dust particles to sneak into our new superconducting accelerator,” said John Schmerge, director of SLAC’s Accelerator Directorate.

 “Crews built the niobium cavities at facilities that are 1,800 or 3,000 miles away from SLAC years before we installed them here. The cavities might have been clean and working well back then, but then you have to wrap them up and ship them across the country on trucks. We then had to install the cryomodules into our tunnel during the fire season in California and weld them together – all of which can introduce dust.”

Niobium is a rare earth metal that was essential to building the accelerator with close to zero resistance.

Electron beam

Now, the team’s new main goal is to improve the quality of the electron beam.

“If you have a nice tight electron beam you get better X-ray production,” Schmerge said. “Whereas if the electron beam is all spread out, you don't get very many photons at the end of the tunnel.”

“Producing a high-energy electron beam gives us a sense that everything is working as we had hoped for,” SLAC scientist Axel Brachman added. “The powerful beam is a glimpse of light at the end of our project’s long tunnel.”

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