photo by Mark Holl; William Graves and Petra Fromme discuss the inner workings of the optical cross correlator for ASU’s forthcoming X-ray free-electron laser.

Laser Trailblazer

Written by Keridwen Cornelius Category: Valley News Issue: October 2018
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Arizona State University is building a laser that could revolutionize everything from cancer treatment to art history.

What can capture a movie of the molecular plot twists in photosynthesis, reveal nearly invisible tumors, help design faster semiconductors and authentic a Picasso? The new laser coming to Arizona State University’s Biodesign Institute. ASU scientists are designing and building the world’s first compact X-ray free-electron laser. The machine is expected to drive game-changing discoveries at ASU, plus attract international scientists and institutions that want to conduct experiments and capitalize on this technology.

“That ASU has committed to this shows that we deserve to be the most innovative university in the U.S.,” says Petra Fromme, director of Biodesign’s Center for Applied Structural Discovery.

Currently, there are five X-ray free-electron lasers (XFELs) in the world – in Germany, Switzerland, Japan, Korea and California. These humongous underground structures, each around 2 miles long, are massively expensive. Stanford University’s cost $1 billion to build and $100 million to operate annually. XFELs are in such demand that scientists wait two or three years to get “beam time,” and 80 percent of applications are rejected. The lucky few accepted get one to five days to conduct their experiment. If something goes wrong, tough – wait another three years.

ASU’s XFEL will be about 30 feet long, cost less than $10 million to build, and operate on $1 million annually. It will employ groundbreaking technology to dramatically shrink both the particle accelerator and the laser.

In the big XFELs, electrons are shot through an accelerator that revs them up to the speed of light. The electrons pass through a long line of magnets with alternating polarity that push them in different directions, causing them to wiggle. When electrons shimmy and shake, they emit X-rays. But these machines produce X-rays with wavelengths so short they’re the size of an atom – so they let us see atoms.

ASU’s compact XFEL replaces those magnets with an ultrafast laser, explains accelerator designer William Graves, an associate professor in ASU’s physics department. “It basically reproduces the magnetic field that’s in this football field-length of magnets in something that’s the diameter of one of your hairs.” Graves and a former colleague at MIT also came up with a totally new way of making an X-ray laser on a miniscule scale by diffracting the electron beam through a crystal.

This compact machine will sacrifice power, but it will produce a more precise beam, Graves says. “I think of the big [XFELs] as a hammer and ours as a scalpel.”

One of the first things this scalpel will probe is the mysteries of photosynthesis. Currently, we essentially have a still snapshot of the mechanisms involved. “But having a static picture of a horse will not tell you how it can run so fast,” Fromme says. “We really have to have a movie” of the molecular actions. With the new laser’s speed and high resolution, plus plenty of “beam time” to take enough images, Fromme hopes to reveal the secrets of plants. This could eventually help scientists construct renewable energy systems inspired by photosynthesis. The laser could also make molecular movies of the way medicines bind to brain receptors, helping drug companies create more effective treatments.

ASU is partnering with Mayo Clinic to use the laser to pinpoint tiny tumors in soft tissue that would likely be undetectable with other medical imaging. They’ll also work with the semiconductor industry to give it the X-ray vision needed to measure and place tiny circuitry to make faster microchips. This accessible laser could also make it easier for museums to peer at works of art sometimes hidden underneath famous paintings – technology that has been used to authenticate a Rembrandt and uncover works by Van Gogh and Degas.

The laser’s parts are being shipped to Biodesign’s new building this semester, and it will take several months to construct. The scientists anticipate making electron beams by spring and X-rays by summer.

5 THINGS YOU DIDN'T KNOW ABOUT X-RAYS
• The first Nobel Prize in physics was awarded to Wilhelm Röntgen for his 1895 discovery of X-rays.

• The X means “unknown.”

• X-rays are a particularly energetic type of light with a very short wavelength.

• Before people knew they were dangerous, X-ray machines were popular carnival attractions.

• Rosalind Franklin’s X-ray crystallography images of DNA helped James Watson and Francis Crick get credit for the discovery of its double-helix structure.