Self standing curved crystals for gamma ray focusing

A Laue lens is an innovative approach to focus x and gamma ray in the energy range from ~60 keV to 600 keV through Laue diffraction by a properly arranged array of crystals. Good candidates as optical elements for such lenses are selfstanding bent crystals, in which the permanent curvature is obtained by a controlled surface treatment. We present a study based on the dynamical theory of x-ray diffraction efficiency of bent Si, Ge and GaAs crystals. We demonstrate that optimizing the curvature and the thickness for a proper diffraction geometry, relatively light Si, Ge and GaAs crystals may diffract with the same or even higher efficiency than higher density mosaic crystals, such as Cu, Ag and Au also permitting to accurately design the diffraction angular range. Thus, the use of low-Z curved crystals in Laue lenses may permit an increase of the lens performance. This opens important opportunities for use in x-ray astronomy for space telescopes and in nuclear medicine for the localization of cancers in the human body.