硬X射线相位光栅的设计与研制

Design and fabrication of hard x-ray phase grating

针对在普通实验室和医院实现40—100keVX射线相衬成像的需求,考虑到成像系统参数、X射线源空间相干特性及光栅衍射效率,设计出硅基相位光栅结构参数.利用我们已发展的光助电化学刻蚀技术研制出直径为5英寸的相位光栅,其空间周期为5.6μm,线宽为2.8μm,深度为40—70μm.在理论分析的基础上,通过提高硅片两端有效工作电压和修正Lehmann电流密度公式,解决了实际刻蚀过程中出现的钻蚀问题.由实验结果可知,本方案对制作大面积高精度相位光栅十分有效。

The x-ray phase grating made on silicon wafer was designed under considerations of the parameters of the phase contrast imaging system,the spatial coherence characteristics of x-ray source and its diffraction efficiency for x-ray of 40-100 keV,which is usually used for phase contrast imaging in laboratories and hospitals.The phase grating with diameter of 5 inch,pitch of 5.6 μm,wall width of 2.8 μm and depth of 40—70 μm depending on the energy of x-ray photon,was fabricated using the technique of photo-assisted electrochemical etching developed in our lab.Two special methods,namely,the enhancement of the voltage applied to the silicon wafer and modification of the current density defined by Lehmann formula,have been used to reduce the lateral etching.A reproducible technique has been developed for fabrication of precise and large x-ray phase grating on silicon wafer.