US: World’s most powerful X-ray laser to get 3,000 times more powerful

The Linac Coherent Light Source (LCLS), the world’s most powerful X-ray laser located at the SLAC National Accelerator Laboratory in the US, is set for a major upgrade that will increase its X-ray brightness 3,000-fold, a press release shared with Interesting Engineering said.

When complete, the upgrade will let scientists explore atomic-scale processes in their search for answers in biology, materials science, quantum physics, and much more.

The LCLS, funded by the Department of Energy (DOE), is the most powerful X-ray machine in the world and was also the first to produce hard or high-energy X-rays with a free-electron laser.

The facility began functioning in 2009 but received a major upgrade in 2023 . It added a superconducting accelerator and magnetic structures called undulators that could produce both soft and hard X-ray beams. Dubbed LCLS-II, the upgrade primed the facility to produce a million X-ray pulses per second.

Now, the DOE has greenlit yet another upgrade, LCLS-II HE (High Energy), which will double the energy of the electron beam coming from the superconducting accelerator, thereby doubling the energy of the X-ray.

What is the LCLS-II-HE upgrade?

The superconducting accelerator in the LCLS-II upgrade consisted of 37 cryogenic modules that can be cooled to -456 Fahrenheit (-271 degrees Celsius) to boost electrons to high energies with negligible energy loss.

For the High-Energy upgrade, the LCLS will get a set of 23 new cryomodules, each containing eight superconducting radiofrequency cavities that will help deliver superior performance.

The modules are built by DOE’s Fermi National Accelerator Laboratory (Fermilab) and the Thomas Jefferson National Accelerator Facility (Jefferson Lab).

“The first cryomodule was a prototype built from a spare from LCLS-II, so we had all the components on hand. Once the production line is going, we have been able to build a unit about every six weeks on average. They are all planned to be installed in the accelerator tunnel in 2026,” said Greg Hays, LCLS-II-HE, Project Director, in an email to IE .

Why upgrade the X-ray laser again?

Considering that the LCLS-II upgrade was completed only in 2023, IE enquired why the HE upgrade was not included simultaneously.

“LCLS-II had to design and install the world’s first continuous wave (CW) superconducting accelerator, meaning that it delivers a continuous stream of pulses at very high repetition rate,” explained Hays in the email.

“We needed to make sure it worked before going too far, and so the decision was taken to install 4 GeV with the LCLS-II project, which is sufficient to drive the “soft X-ray” science program at LCLS.”

“Since then, superconducting accelerator technology has matured, enabling the LCLS-II-HE project to double the energy of the accelerator from 4 to 8 GeV without doubling the number of components. This will allow us to access the “hard X-ray regime” at this high repetition rate for the first time.”

When will it be ready?

Achievement of the First Light is predicted for late 2027 but could extend to 2030 as well. “The first activity will be to determine how well the new beam is performing,” added Mike Dunne, LCLS Director, in the email. “We will then move to an “Early Science” period that engages a broad cross-section of the user community, and then onto individual user experiments.”

However, the upgrade does not mean the LCLS-II won’t be available for experiments. Since the facility has two accelerators and only the superconducting accelerator is being upgraded, it can continue functioning using the normal conducting accelerator.

“If the LCLS-II upgrade enabled a high-quality movie camera capable of capturing clear and detailed images, the LCLS-II-HE upgrade greatly boosts that camera’s resolution and sensitivity. Scientists will be able to image the atomic-scale motion of materials, chemical systems and biological complexes to address some of the most critical challenges facing our society.”