New Laser Could Create Atomic "Movies"

The new X-ray laser at SLAC National Accelerator Laboratory could one day produce atomic "movies."

Watching how plants transform sunlight into sugars, potentially leading to new fuels. Understanding how magnetic fields switch back and forth, a key step in developing faster computers.

Scientists have big hopes for the world’s first X-ray laser, a $420 million project unveiled Monday afternoon in Menlo Park.

“Science and technology has formed a lot of the basis of the wealth in the United States over the past several decades,” U.S. Energy Secretary Steven Chu told a standing-room-only audience at the SLAC National Accelerator Laboratory, where the laser was dedicated. “And we will need science and technology to solve some of our most pressing problems, including that of transitioning to clean energy and solving our climate problem.”

U.S. Energy Secretary Steven Chu talks to reporters. Also in the photo, Rep. Zoe Lofgren and Rep. Mike Honda . Courtesy of SLAC.

Chu said that the Obama administration wants to double science funding over the next decade.

Construction began on the project, known as the Linac Coherent Light Source in 2006, led by SLAC National Accelerator Laboratory, Argonne National Laboratory and Lawrence Livermore National Laboratory. Stanford operates the SLAC National Laboratory for the Department of Energy, which provided the funding.

Creating atomic "movies"

The light source is the first of a new generation of imaging tools that produce X-ray pulses – like bursts of strobe lights – that are 100 to 1,000 times shorter than was previously possible. Scientists hope that the short pulses will allow them to take photos of atoms moving around, a process that happens in a period of time so short that it’s measured in a unit of time called a femtosecond, which lasts one millionth of one billionth of a second.

Flashing these very short pulses of X-rays onto atoms in motion is akin to using a very fast shutter speed in a still camera to make a crisp photo of a moving object, said SLAC director Persis Drell.

“You can see what atoms are doing, on the time scale they’re actually doing things, which is femtoseconds,” she said. “And no one’s ever come close to that before.” Scientists hope that one day these atomic “photos” will form the basis of atomic stop-motion “movies.”

Turning a nuisance into a powerful X-ray machine

Light sources are machines that use bright X-rays to make images. They’ve been around since the 1960s and have their origin in the particle accelerators of that era, where fundamental particles like electrons were smashed into other particles to investigate the tiny constituents of the atom. Researchers noticed that as the electrons sped up inside the accelerators, they let off X-rays, which were a nuisance because they meant that the electrons were losing energy.

But scientists quickly figured out that they had a powerful tool in their hands. These X-rays were several thousand times brighter than the ones used to make images of the human body in a hospital. Once researchers learned how to harness them, they had machines that could easily make images of the precise structure of tiny things like water molecules, viruses, and proteins inside the human body.

“From their structure we try to infer how they work,” said Joachim Stohr, director of the new light source. This has helped with drug development, he said.

“What we would love to do is take a movie of how a drug can inhibit a reaction or initiate a reaction,” Stohr said.

In this artist's rendition, the X-ray laser hits a biological sample and photographs it at the same time. The blue and orange square shows what a "photo" would look like. Courtesy of SLAC.

One billion times brighter

The new light source not only produces shorter pulses of X-rays than existing light sources at SLAC and Lawrence Berkeley National Laboratory. These pulses are also a billion times brighter because all the photons, or packages of light, are made to act together, in what’s called a “coherent” way. This is what makes the new machine a laser, said SLAC physicist Paul Emma, who was in charge of getting the new light source up and running.

The new machine was turned on in April, 2009 and has operated as expected. Japan and Germany are also building X-ray lasers. And the Department of Energy has given the go-ahead for the design of phase two of the SLAC X-ray laser.

Putting SLAC’s linear accelerator to new use

To produce X-ray pulses, the new machine starts out with electrons that are accelerated to near the speed of light in the last third of SLAC’s two-mile linear particle accelerator. That linear accelerator, which was famous for being the longest in the world when it opened in 1968, was used to confirm the existence of the fundamental building blocks of the atom, called quarks. The linear accelerator is no longer used for particle physics experiments.

As the electrons travel down the linear accelerator, they’re squeezed into small bunches. Then a series of magnets called undulators, organized in a 430-foot line, wiggle the electron bunches back and forth and shake off the intense X-rays.

“This has to be done exquisitely precisely,” said SLAC director Drell. “Those undulators have to be aligned to maybe a fifth of the diameter of a human hair. It’s a major technical feat to get everything to line up to make this work.”

Monday’s event was something of a homecoming for Chu, a former professor of physics at Stanford and director of Lawrence Berkeley National Laboratory until he was tapped by President Obama last year to run the Department of Energy.

Chu was part of committees in the 1990s that studied the viability of laser projects like the one he dedicated Monday. He won the Nobel Prize in Physics in 1997 for research into the cooling and trapping of atoms with laser light.

Of the new laser, Chu said that “it feeds all the technologies, from the material science that is needed for the next generation of semi-conductors and computers, to the pharmaceuticals, the biotechnology, and finally, to the energy technologies that we’re going to have to develop in the future.”

Video: SLAC National Accelerator Laboratory Director Persis Drell explains how the new X-ray laser could help scientists learn more about how plants turn the energy from the sun into fuel.

More video:
Watch QUEST TV's segment about the history of SLAC National Accelerator Laboratory and Lawrence Berkeley National Lab, called Homegrown Particle Accelerators.