Comparison Of X-ray Imaging By A Fresnel Zone Plate And Projection-type Phase Contrast Imaging

Laser driven inertial confinement fusion use laser or X-ray ablation to compress ICF target to abtain high density plasma. In the process of compression, hydrodynamics instability of the plasma seeded by rough ablator or fuel layers can reduce the compression efficiency. Current specifications of the ablation layer and the fuel layer require less than 1 μm rootmean-squared roughness. X-ray backlight imaging is often used to diagnose these defects, and spatial resolution of imaging is required to reach 1-2 μm.X-ray diffraction imaging has great potential for achieving near-diffraction-limited spatial resolution. We discuss the influence of Fresnel zone plate (FZP) ring number and number of the central ring blolcked FZP on imaging quality. The results show that the number of FZP’s ring is higher, the imaging contrast is higher, and the number of blocked ring is higher, the imaginag quality is worse. In addition, we simulate the FZP imaging by visible extended light source.We use analytical and numerical approaches to compare effect of Fresnel zone plate (FZP) imaging and projection-type phase contrast imaging, and the energy of X-ray used to backlight irradiation is 4.5 keV of Ti Ka line and 8.9 keV of Cu Ka line. The results show that the spatial resolution of FZP imaging is better than 1 μm, and it is beneficial to use large scale light source. Projection-type phase contrast imaging is use for high transmission or weak absorption object. It has been proven can achieve high spatial resolution of a few microns. We also use numerical approach to study phase contrast imaging in the case of thin film target with the thickness fluctuation and spatial density modulation target with the microfocus x-ray source. The theoretical contrast of images is consistent with simulation in the situation of point source. We also discuss the influence of the size of source and imaging distance on contrast and spatial resolution.