Old LPs Find New Use in X-Ray Optics
Aaron J. Hand
STOCKHOLM, Sweden -- In trying to develop a cheap way to focus x-rays, perhaps it should be no surprise that researchers turned to German technopop group Kraftwerk for help. The scientists bought one of the band's albums to cut up and form into a sawtooth refractive lens.
Besides its low cost, the Kraftwerk album was chosen because of its very long songs, enabling the researchers to cut long sections with uniform grooves and no interruptions, said Björn Cederström, the physicist who came up with the idea. Ultimately, however, he and his colleagues at Sweden's Royal Institute of Technology and Lawrence Berkeley National Laboratory in Berkeley, Calif., had to press their own vinyl albums for their experiments because standard LP grooves were not deep enough.
Refractive focusing is inherently inexpensive and simple, Cederström said, because the demand on surface quality is much lower than it is for reflective and diffractive techniques. Add to that a technique that relies on cheap vinyl records, and "it is really a bargain," he said.
As noted in the team's report in the April 27 issue of Nature, the lens has a focal length of 22 cm for 23-keV x-rays. Because the relatively small lens restricts the beam's capture angle, it is best suited to microbeam applications, Cederström said. "It should be rather useful in synchrotron facilities, which produce this kind of beam," he said. "I think crystal diffraction experiments, where you need a low-divergence beam upon a small sample, is a promising application."
The researchers are testing a similar lens that they fabricated in beryllium, which offers better performance because it has a smoother surface and less x-ray absorption than vinyl. Each lens costs a few hundred dollars, Cederström said.
Plans to commercialize the lens are imminent. The researchers have established Mamea Imaging, a company that will use the new lens in mammography screening systems, Cederström said.
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