Study Of Key Devices And System Of Large Field-of-view Grating-based X-ray Differential Phase Contrast Imaging

Among X-ray phase-contrast techniques, grating-based X-ray differential phasecontrast (DPC) imaging using conventional X-ray tube sources is the most prominentone for widespread applications in the case of acquisition of large-format,high-quality key devices, mainly X-ray gratings in mass production. So far, LIGA(Lithography, Electroplating, and Molding) is the main method in the fabrication ofabsorption gratings with a super high aspect ratio. Additionally, the noble metal goldis choosed as the absorbing material. Thus, These existing processes and material leadto a high cost and limit the broad dissemination of these components for DCPimaging.This thesis focuses mainly on the design and fabrication of key components ofX-ray DPC imaging. We proposed and developed a micro-casting process. Thisprocess is feasible for acquirement of X-ray absorption gratings with a low cost and ahigh performance. Based on the design of the absorption gratings structures,photo-assisted electrochemical etching was used for the formation of grating structures in4and5in. n-type <100> silicon wafer. Then, a layer of SiO2was covered on the wall surface ofstructures by dry thermal oxidation, which we called surface modification, to improve theinfiltration. This process would make the molten bismuth fill smoothly into thesestructures via surface tension. Bismuth was employed as absorption grating materialinstead of gold firstly proposed by us because of its great mass absorption coefficient,low cost, and broad environmental compatibility. Furthermore, our micro-castingprocess provided bismuth absorption gratings with characteristics of a high degree offilling, a clean surface, and a high yield.Additionally, The improvement of phase grating structure made its surfacetopography well and led to no wall collapsing anywhere. Then, a structured CsI(Tl)X-ray scintillator was manufactured on a5in. silicon wafer by a vacuum vaporplating process. With regard to the low brightness of X-ray scintillator functioningalso as analyzer grating proposed and fabricated by us, two ways were provided toimprove that. One way is to change the longitudinal to the transversal filling, andsome complementary approaches attached to make a high degree of filling ofscintillator CsI(Tl), another way is to change the grating structure to increase thefilling degree, which would result in an enhancement of brightness by10%.Finally, By using these components, a low-cost X-ray DPC imaging system was constructed, and some phase-contrast images were obtained by using the two-stepphase stepping method. The results demonstrated that all of our components meet therequirements of the grating-based X-ray DPC imaging.