Researchers from Imperial College London, the University of Michigan and Instituto Superior Téchnico Lisbon have described a tabletop instrument that produces synchrotron X-rays whose energy and quality rivals that produced by some of the largest X-ray facilities in the world.
While the development and use of high-energy light sources to probe the details of a wide range of materials for research and commercial purposes is a rapidly growing area of science and engineering, high power, high quality X-ray sources are typically very large and very expensive. To take one example, the Diamond Light Source synchrotron facility in the UK, has a circumference of 500 metres and cost £263 million to build.
The researchers have demonstrated that they can replicate much of what these huge machines do, but on a tabletop. Their micro-scale system uses a jet of helium gas and a high power laser to produce an ultrashort pencil-thin beam of high energy and spatially coherent X-rays.
“This is a very exciting development,” said Stefan Kneip, lead author on the study from the Department of Physics at Imperial. “We have taken the first steps to making it much easier and cheaper to produce very high energy, high quality X-rays. Extraordinarily, the inherent properties of our relatively simple system generates, in a few millimetres, a high quality X-ray beam that rivals beams produced from synchrotron sources that are hundreds of metres long. Although our technique will not now directly compete with the few large X-ray sources around the world, for some applications it will enable important measurements which have not been possible until now.”
The X-rays produced by the new system have an extremely short pulse length. They also originate from a small point in space, about 1 micron across, which results in a narrow X-ray beam that allows researchers to see fine details in their samples. These qualities are not readily available from other X-ray sources and so this system could increase access to, or create new opportunities in, advanced X-ray imaging. For example, ultra-short pulses allow researchers to measure atomic and molecular interactions that occur on the femtosecond timescale.
Zulfikar Najmudin, one of the researchers at Imperial, said, “We think a system like ours could have many uses. For example, it could eventually increase dramatically the resolution of medical imaging systems using high energy X-rays, as well as enable microscopic cracks in aircraft engines to be observed more easily. It could also be developed for specific scientific applications where the ultrashort pulse of these X-rays could be used by researchers to freeze motion on unprecedentedly short timescales.”
In a study published this week, the researchers describe for the first time the technical characteristics of the beam and present test images that demonstrate its performance.
Najmudin said, “Our technique can now be used to produce detailed X-ray images. We are currently developing our equipment and our understanding of the generation mechanisms, so that we can increase the repetition rate of this X-ray source. High power lasers are currently quite difficult to use and expensive, which means we’re not yet at a stage when we could make a cheap new X-ray system widely available. However, laser technology is advancing rapidly, so we are optimistic that in a few years there will be reliable and easy to use X-ray sources available that exploit our findings.”
References
Bright spatially coherent synchrotron X-rays from a table-top source
Kneip, S. et al.
Nature Physics. Published online: 24 October 2010
http://dx.doi.org/10.1038/nphys1789
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