Guiding Gamma Rays

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Science  09 May 2008:
Vol. 320, Issue 5877, pp. 718-719
DOI: 10.1126/science.320.5877.718d

Early exposure in high-school science labs to geometrical optics with lenses and mirrors fosters wide familiarity with how to focus and manipulate light in the visible spectrum. A very broad range of convenient focal parameters is available at these wavelengths. As the energy of the photons increases and their wavelengths shrink into the x-ray and gamma-ray regimes, however, conventional lenses and mirrors no longer work. Instead, such high-energy photons must be guided along their path by shallow-angle reflection from specially designed mirrors. Because of the small angles required to avoid absorption losses, the typical focal distances involved are on the order of 10 m or so. Though manageable for the likes of large, Earth-based observation stations, these focal parameters are rather unwieldy for medical imaging, space-based observatories, or mobile radioactive material detectors. Tournear et al. show that multilayered stacks of gold-palladium and polymer films deposited on a curved silicon substrate can be used to effectively guide gamma rays with a much smaller focal length. Demonstrating the technique for gamma rays of 122 keV, they claim that the focal lengths can be shrunk down to 1 m or less for radiation in the ∼100-keV to low-MeV range. — ISO

Appl. Phys. Lett. 92, 153502 (2008).

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