High-Z crystals for gamma-ray optics

In a Laue lens a large number of crystals are disposed on concentric rings such as they diffract via Bragg-diffraction the incident gamma-rays onto a common focal spot. Compact structured high-Z mosaic-crystals are among the most efficient diffraction media for the domain of nuclear astrophysics (i.e. 300 keV <= E <= 1.5 MeV). We have studied the potential of various high-Z crystals such as Ir, W, Au, Ag, Pt, Rh and AsGa for a Laue lens application. The diffraction performance of gold, silver and platinum crystals have been measured during runs at the European Synchrotron Radiation Facility and in a reactor-beamline at the Institut Laue Langevin, Grenoble in France. Several of the tested high-Z materials show outstanding performances with reflectivities reaching the theoretical limits for mosaic-crystals, and hence open the way towards efficient focusing optics at MeV energies.