Mathematical Modeling And Experimental Research On4-window Type CGLSI

In the Inertial Confinement Fusion(ICF), laser or ion beam, acting as driving source, provides high energy uniformly on the capsule which is filled with deuterium-tritium. So the density uniformity and optical thickness of D/T layer are crucial parameters for successful ignition. In order to acquire these crucial parameters, a newly designed4-window type Cross Grating Lateral Shearing Interferometer(CGLSI) is established. The content of the thesis can be divided into three parts based on this system.The first part is about establishing a mathematical model for CGLSI and the deduction of crucial parameters for cross grating and order-selecting window which are key components in CGLSI. The expression of grating constant d which is a crucial parameter in cross grating and shearing ratio β can be obtained with the employment of grating equation and the definition of shearing ratio. The intensity distribution of light on order-selecting window is calculated based on complex amplitude distribution of spherical wave and Fresnel diffraction formula.The second part is about computer simulation on crucial parameters of cross grating and order-selecting window. Four feasible grating constant are d=20μm,d=25μm,d=40μm and d=50μm which is based on the expression about grating constant d and shearing ratio β as well as the restrictive condition for shearing ratio. The intensity distribution of light on order-selecting plus four feasible grating constant determine four types of order-selecting window and their parameters respectively.The third part is about experimental research on CGLSI. The devices in the experiment are designed and fabricated based on the simulation results in the second part. During the experiment, one-dimensional grating and two-dimensional cross grating with different grating constant and their corresponding order-selecting windows are employed. The interferograms are obtained on CCD through the adjustment of the device. The contrast ratio of fringes which is acquired through the processing of interferograms is high and stable on both conditions of one-dimensional grating and two-dimensional cross grating. The reasonability in the first part (mathematical modeling) for the establishment of cross grating and order-selecting window as well as for the relationship between grating constant and shearing ratio plus the expression for the intensity distribution of light on order-selecting are confirmed. The reasonability in the second part (computer simulation) for the parameters of cross grating and order-selecting window is also confirmed.