级联式平面抛物面型X射线组合折射透镜的设计与制作

X射线组合折射透镜(CRL)已逐步成为同步辐射光源下X射线聚焦光学器件的标准配件之一,它具有结构紧凑、易调节校准、适用光子能量范围大等优点.本文设计了一种级联式平面抛物面型CRL,它将N1个具有较大抛物面几何孔径(R0)的折射单元I与N2个具有较小抛物面顶点曲率半径(R)的折射单元II级联,以解决常规CRL设计过程中焦斑尺寸与透过率的矛盾.采用PMMA材料,利用LIGA技术制作了一组级联式平面抛物面型CRL,其中折射单元I的主要结构参数为N1=15,R1=200μm,2R01=564μm;折射单元II的主要结构参数为N2=20,R2=50μm,2R02=140μm.在上海光源同步辐射线束上,所制作的级联式平面抛物面型CRL实现了对初始光斑尺寸为200μm×100μm的入射X射线的一维聚焦,测试得到的焦距为1.052 m,横向焦斑尺寸为24.9μm@8 keV,透过率为2.19%.

Design and fabrication of cascaded X-ray planar parabolic compound refractive lens

Due to its attractive features such as compact size, simple to align and wide working range of photon energy, the X-ray compound refractive lens (CRL) has gradually become one of the standard accessories to focus the X-ray beams from the synchrotron radiation light source. In this paper, a cascaded planar parabolic CRL is designed and fabricated. The novel CRL is composed of type Ⅰ and type Ⅱ refractive elements in order to achieve a small spot size while maintaining the transmission. In type I refractive element, the parabolic geometry aperture (R₀) is large, while, in type Ⅱ refractive element, the radius of curvature (R) at the parabolic vertex is small. So N₁ numbers of type I and N₂ numbers of type Ⅱ refractive elements are cascaded to form a single-chip CRL. A cascaded X-ray planar parabolic CRL is constructed using PMMA material by means of LIGA techniques. The main structural parameters of type Ⅰ refractive elements are: N₁=15, R₁=200 μm, 2R₀₁=564 μm. The main structural parameters of type Ⅱ refractive elements are: N₂=20, R₂=50 μm, 2R₀₂=140 μm. The cascaded planar parabolic CRL is tested on the beam line whose original incident X-ray spot is 200 μm×100 μm at Shanghai synchrotron radiation facility. The measured lateral focusing spot size is 24.9 μm@8 keV, the transmission rate is 2.19% and the focal length is 1.052 m.
Keywords： compound refractive lenses X-ray optics parabolic lenses