May 21, 2004  




Compact Light Sources

By Mason Inman

Today there’s a gap between conventional laboratory x-ray sources and state-of-the-art facilities such as SSRL, comparable to the difference between a laser and a light bulb. Synchrotron facilities produce intense beams of nearly parallel, monochromatic light over a wide range of wavelengths. Most laboratory x-ray sources, on the other hand, produce much less intense, lower quality beams.

Ron Ruth (ARDA) is working to close this gap by developing a tabletop x-ray source that can fit in a typical lab, but that will provide x-rays comparable with some of the beamlines on the recently-retired SPEAR2 synchrotron.

To bring this idea to fruition, Ruth founded Lyncean Technologies, Inc., in 2001 with two former SLAC employees, Jeffrey Rifkin and Rod Loewen. The company is funded by more than $7 million in grants from the Protein Structure Initiative, a project administered by the National Institute of General Medical Sciences, a branch of the National Institutes of Health. Ruth made the first public announcement of the device on April 16 at the Keystone Structural Genomics Conference, stating that the company has just begun constructing a prototype and plans to start testing in early 2005.

The technology is under license from SLAC. If it works as planned it will be able to supply x-rays for a wide variety of work including protein-structure analysis and soft-tissue imaging. “The Compact Light Source (CLS) can address the full spectrum of scientific applications which require the type of x-ray beams available at the large synchrotrons, except those that require the highest flux,” Ruth said.

Ruth makes an analogy, comparing facilities such as SSRL to supercomputers, and current laboratory x-ray sources to hand-held calculators. The CLS would be like a personal computer or workstation—a big step up from the calculator, but still affordable and powerful enough for many applications.

“The CLS will boost productivity by providing high-quality x-ray beams right at the fingertips of researchers in all fields of x-ray science," Ruth said. "Some of the most exciting future applications for our source are in health care. New medical imaging techniques that provide exquisite detail of soft tissue are being developed at synchrotron beamlines today. The CLS will bring these out of the laboratory and into the hospital.”

At facilities such as SSRL, x-rays are produced by forcing a beam of electrons through a series of magnets that causes the electrons to undulate, accelerating them side to side as they travel around the synchrotron's ring. Any time a charged particle such as an electron is accelerated, it gives off light, and SSRL was designed so the electrons would give off a range of frequencies of light, from x-rays to infrared.

The CLS will undulate the electrons using a laser rather than magnets. Though the electrons will zip around this tabletop device with much less energy than those in SSRL, they will also get shaken more vigorously by the laser. This technique, based on work by Ruth, Loewen and Zhirong Huang (ARDA), should produce a high-quality x-ray beam comparable to those from some large synchrotrons. The CLS’s x-ray beam will have much lower intensity overall, but the quality should be in the ballpark of the large facilities—but without the source being the size of a ballpark.



The Stanford Linear Accelerator Center is managed by Stanford University for the US Department of Energy

Last update Tuesday May 18, 2004 by Emily Ball