Journal Article Research Support, Non-U.S. Gov't X-ray diffraction imaging X-ray free-electron laser coherent X-ray diffraction imaging hard X-ray ptychography phase retrieval structure analysis of non-crystalline particles 9007-43-6 Comparative Study Cytochromes c Fraunhofer diffraction beam emittance biological cells cryogenic experiments deep neural networks depth of focus diffraction limit formula-driven supervised learning humidity control microbeam non-crystalline samples phase problem phase retrieval calculation phase space phase-retrieval calculation spatial resolution structural analysis structural analysis of non-crystalline particles subgradient projection