Lensing gamma rays

Gamma ray lenses? A team at Ludwig Maximilian University of Munich created a silicon prism that slightly deflected gamma rays with an effective refractive index of 1.000000001. Using gold instead of silicon should increase it quite a bit: If this is Delbruck scattering as they think, then since the scattering goes as Z to the fourth power (Z is the atomic number of the nucleus), the refractive index would go to 1.000001. Not big, but it could be useful.

X-rays can be focused, apparently using multiple very small lenses, or using "zone plates" (or see this). I think you could get better luminosity by using x-ray channeling in slices of crystal tilted at angles that increase with distance from the center of the lens--but I never figured out how to fabricate one easily/cheaply, and the best focus you'd get would be of the order of the size of the crystal slices. (I was thinking of uses in dental x-ray systems, where you could increase the intensity in the interesting direction without increasing the power and total radiation dose.)

Update: FWIW, I didn't remember anything about Delbruck scattering when I read this; all I know I learned from looking it up for the occasion. And the "SciTechDaily" site made hash of the story, so I didn't link them. Gamma ray wavelengths are smaller than the size of atoms, so it isn't surprising that any sort of bending would be small.