Improvement of Coherent X-ray Imaging and Pump-Probe Diffraction Techniques Based on X-ray Free Electron Lasers

Abstract

In this thesis, enhanced data processing methods in coherent X-ray diffraction and XFEL pink pump probe, are studied. In chapter 1, brief characteristic of XFEL and its develoment is discussed. In chapter 2, methods to overcome the innate problem in CDI using discretized in finite range diffraction pattern are discussed. Without using the correct input for CDI, the aliased diffraction pattern, reconstructed images in CDI holds artifacts that resembles Gibbs ring like artifact and long-ranged artifacts. Corrector factor is devised to approximate aliased diffraction pattern with interpolation kernel. Further, exclusion of Fourier constraints is discussed with correction factor. The effectiveness of both suppressing the artifacts are confirmed in computer simulation and actual data. In chapter 3, enhancing resolution of X-ray diffraction pattern using XFEL pink beam is discussed. The XFEL pink beam offers excellent photon flux but suffers from shot by shot energy jitters which lowers the resolution. Without setting supplementary spectrometer or monochrometer, method to assign each shot energy via observed sample intrinsic structure in its diffraction pattern is presented. Further, its way to implement in pump-probe X-ray diffraction scheme is proposed and applied actual pump-probe experiment data with XFEL pink beam.