Design and characteristics of multi-grating modulation screen for desktop X-ray system

The desktop X-ray system has limitations such as low flux and poor coherence. It faces great challenges in application scenarios such as microscopic imaging and high-precision measurement. Fourier-transform ghost imaging (FGI) has low requirements for the coherence of the light source. Using this principle, multi-angle FGI based on spatial correlation can effectively improve the imaging efficiency and is suitable for desktop X-ray systems. However, this technology is still in the theoretical stage, and there is a lack of effective devices to modulate X-rays and form focused multiple beams. To this end, a multi-grating modulation method is proposed in this work. The partially coherent radiation of the X-ray source is modulated by arranging multiple sub-gratings in a specific direction. The X-ray emitted by a single sub-grating is spatially coherent light, and the X-rays between the sub-gratings are incoherently superimposed at the sample position to form a focused multi-angle beam. This effectively improves the flux utilization of the desktop system. The modulation principle of multi-grating is described theoretically, and the key design parameters and their selection basis are clarified. Through numerical simulation, the modulation characteristics of partially coherent X-rays in the propagation process behind the modulation screen are systematically analyzed. By optimizing the parameters such as the size, material and thickness of the sub-grating, the influences of the sub-grating on the size, uniformity and diffraction efficiency of the focused spot are investigated. The results show that when the sub-grating size matches the spatial coherence size of the X-ray source, the focusing effect of the beam can be significantly improved, and a smaller and uniform focal spot can be obtained. Based on the theoretical and simulation results, a gold multi-grating modulation screen is designed and fabricated for the liquid target X-ray source. The simulation and theoretical predictions will be validated experimentally, once the experimental conditions are met. The design and implementation of the modulation screen provide effective support and a feasible way for multi-angle diffraction imaging and related applications in miniaturized X-ray systems.