Scientists turn on world's biggest x-ray machine under I-280

July 25, 2010 12:00:00 AM PDT
After a decade of construction, scientists at the Stanford Linear Accelerator have turned on the world's biggest x-ray machine. It's a 3-mile long laser beneath Highway 280 on the Peninsula - call it the Hubble Telescope for atoms.

"Not every accelerator I've worked on has turned on as quickly as this one. It was a dream come true." The man expressing delight is John Galayda, who was in charge of designing the new LINAC Coherent Light Source.

Stanford Linear Accelerator physicist Alan Fisher agrees. "The entire group has been excited and amazed that this machine has worked as beautifully as it has."

The machine is a laser crossing Highway 280 two stories underground. The first to produce hard x-rays -- x-rays that enable us to see processes that were only a dream 20 years ago.

"People have already been working on taking images of viruses," says Fisher. "And we're interested in proteins and DNA, and things of that sort."

And not just snapshots. The beam pulse is so fast that an image is captured before molecules have time to fly apart. That means the first atomic movies.

"The x-rays are so intense we can take flash holograms of molecules. The x-ray pulse here is so short," adds Galayda, "that atoms don't have time to move very far. In fact, we're getting to the point now where we can see the motion of the electrons whizzing around the atom."

First, the original SLAC source generates a packet of electrons the size of a grain of rice and shoots it through a tube the size of a drinking straw. Now, imagine stretching that straw to the length of three football fields and keeping it so straight that the grain of rice never touches the sides of the straw! Those electrons generate x-rays which are collimated (lased) into a small chamber. Six more like it one are planned.

The LINAC Coherent Light Source (LCLS), funded by the U.S. Department of Energy, is just getting started. And already it has scientists around the world beaming.

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