Curved crystals as optical elements for focusing X- and γ rays in a Laue lens

Curved crystals as optical elements for focusing X- and γ rays in a Laue lens Abstract This thesis is devoted to achieve a method to realize bent crystals in order to diffract hard X- and γ rays with high-efficiency. A simple and economical method that would lead to the production of accurate and homogeneous bent samples is presented. In fact, a homogeneous curvature is a necessary condition for the diffraction of the radiation with high efficiency and resolution. Furthermore, an appropriate physical model is given, to foresee the curvature of the samples as a function of the production parameters. Several silicon and germanium samples were bent and pre-characterized at the Sensor and Semiconductor Laboratory (SSL) of Ferrara, Italy. The focusing capabilities of the crystals were tested with monochromatic and polychromatic X- and γ rays at the European Synchrotron Radiation Facility (ESRF) and at the Institut Laue-Langevin (ILL) in Grenoble, France. Investigations and experimental validations of diffraction with unusual crystal configurations are described. Furthermore, two proposals of Laue lens are given. Such proposals were theoretical obtained with LaueGen, a genetic algorithm written for this purpose. Finally, the performance of these simulated Laue lenses are shown and compared with the data available in the literature. The work of thesis was carried out within the Laue project, which is a project financed by the Italian Space Agency (ASI). The final aim of the Laue project was the realization of a prototype of Laue lens composed of germanium and gallium arsenide bent crystals. In particular, the realization and the precharacterization of the germanium samples were performed during this Ph.D. period.