Laboratory phase contrast nano-imaging using X-ray waveguide

Abstract

X-ray phase contrast imaging is nowadays an established technique used to investigate the inner structure of materials in various scientific areas. The problem remains the limited applicability of such technique in a common laboratory setup. The work of the present thesis has been developed within this framework. The activity was focused on the Propagation based Phase Contrast Imaging technique implemented by the use of the X-ray WG optics. When and why phase contrast is preferable respect to the standard absorption technique was clarified in the first part of Chapter 1, while the fundamental concepts and equation of the propagation based method was described in section 1.5.5. In Chapter 2 the WG basic theory was reported. Particularly fascinating is the possibility to use the WG as a coherent filter exploiting the self-imaging effect as described in sections 2.6 and 2.7. The fabrication process for planar X-ray WG was described in Chapter 3. The adjustments of the various steps necessary to obtain a working air guiding layer with a dimension of few hundred nanometers were not a trivial issues. In Chapter 4 the WG based phase contrast microscope built up at the X-ray laboratory of the Institute for Photonics and Nanotechnology of Rome was described. Particular attention was focused on the choices made on the geometrical configuration of such a microscope. Very interesting are the measurements reported in sections 4.5 and 4.6 about the dependence of the resonance spots visibility and the microscope resolution on the quality of the WG entrance gap illumination. A first step forward to transfer X-ray coherent methods from large scale synchrotron radiation facilities to standard laboratory setups was made in Chapter 5. To our knowledge, no holography reconstruction results with such small resolution have ever been obtained in a standard laboratory. Finally in Chapter 6, very interesting measurements on human hair fibers were reported.