Snapshots and Scrapbooks

Raimund Fromme, Arizona State University

A reconstructed image of the Photosystem I complex.

This is the season for shopping and stuffing and scrapbooking: For making memories and sharing them with friends.

That's what researchers at the Office of Science's SLAC National Accelerator Laboratory are doing as well. But they're using what in some senses is the fastest X-ray camera on the planet, the Linac Coherent Light Source (LCLS), an X-ray free electron laser. And they're sharing its ‘snapshots' in order to speed scientific progress.

The LCLS, the world's first hard X-ray laser, uses a kilometer-long (about six-tenths of a mile) linear accelerator to produce pulses that are tens of billions times brighter than the conventional X-ray machines used in hospitals. Its "shutter speed," the speed with which it captures events, is less than 100 femtoseconds. That's about the time it takes light to travel the width of a human hair, or about 3-4 trillion times faster than the blink of an eye (figuring that an average eye-blink happens in about 300-400 milliseconds).

Those strobe-like pulses from the X-ray laser are so fast that they can capture the action of atoms and molecules, and ultimately, allow scientists to make molecular movies. Single-shot diffraction images can reveal tiny structures, like those of viruses and proteins, in incredible detail. The X-ray pulses can also penetrate places that visible light cannot, revealing important details that were previously hidden in the shadows.

Enlarge Photo

$X-ray diffraction pattern of a single Mimivirus particle imaged at the LCLS$ Tomas Ekeberg, Uppsala University

X-ray diffraction pattern of a single Mimivirus particle imaged at the LCLS. In this study, the X-ray pulse lasted a millionth of a billionth of a second and heated the virus to 100,000 degrees Celsius, but not before this image was obtained.

But pulling out that detail is exceptionally difficult, since the LCLS doesn't capture conventional images. Instead, using a suite of sophisticated detectors, it collects the X-ray pulses that scatter off the sample in all directions. So the data it registers needs to be filtered and interpreted. Moreover, the laser can produce up to twenty terabytes (trillions of bytes) of data each day, only a small fraction of which might have the information for which scientists are searching.

So, in order to accelerate new discoveries in the field, a group of scientists who use the LCLS – led by Ilme Schlichting and Filipe Maia – decided to share their images with anyone who would like a look. They've set up the Coherent X-ray Imaging Data Bank (CXIB) http://cxidb.org/, a site where scientists from all over the world can post X-ray images, or examine those already posted, looking through the copious sets of data for new ideas and new insights. The databank already contains some 15 data sets, including information from viruses, yeast and nanoparticles. And the data sets are set up in a standardized format, which should reduce compatibility problems and further speed the creative process of discovery.

When looked at closely, seasonal snapshots show more than just the present (or a lot of presents!), they show potential, the promise of the year ahead. The same is true for the information researchers are adding into the CXIB. They're showing the way to new insights and potential new benefits. They're a gift from the Office of Science that will keep on giving.

For more information on the SLAC National Accelerator Laboratory, please go to: http://www.slac.stanford.edu/. And for more information on DOE's Office of Science, please go to: http://science.energy.gov/.

Charles Rousseaux is a Senior Writer in the Office of Science.