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
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
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