Anodic bonding to manufacture LAUE lenses for high energy astrophysics

The hard X-/soft gamma-ray band is still not well explored in astrophysics in spite of several unanswered science questions that can only be settled in this energy band, such as the origin of the 511 keV positron annihilation line from the Galactic Center region. The main reason is that this band has been explored so far with non-focusing instruments, that can achieve a limited sensitivity and angular resolution. Our goal is the development of a focusing telescope based on a Laue lens made of bent crystals of Silicon and Germanium, that diffract photons in the 50-700 keV band, with unprecedented angular resolution and sensitivity to continuum spectrum and to lines. Here some result will be reported concerning the elastic bending of the crystals by pressing them on substrates with one of the two main surfaces worked in order to get the same curvature of the lens. This is achieved thanks to accurately anodic bonding them to these substrates, avoiding/without the use of glue, in such a way to satisfy the required angular orientation of the crystals in the lens.