Design And Fabrication Of Wolter-Ⅰ X-Ray Microscope Mandrel For Replication

Compared with traditional KB microscope and pinhole camera,Wolter-Ⅰ X-ray microscope has better off-axis imaging ability and larger collecting area.Therefore,Wolter-Ⅰ microscope has a broad application prospect in the field of X-ray imaging.At present,the main challenge restricting the application of Wolter-Ⅰ microscope is the fabrication of Wolter-Ⅰ mirror.The reflecting surface of Wolter-Ⅰ microscope is the inner surface with narrow structure.This makes the direct processing method cannot be used for Wolter-Ⅰ microscope.Nickel electroform replication method becomes the main fabrication method of Wolter-Ⅰ microscope.For the replication method,it is necessary to obtain a high-precision ultra-smooth mandrel.After the mirror is separated from the mandrel,Wolter-Ⅰ mirror with reproduction of mandrel topography can be obtained.The main research object of this paper is Wolter-Ⅰ X-ray microscope mandrel used in nickel electroforming replication method,focusing on its size design and tolerance distribution,mandrel turning,surface polishing and surface measurement.1)For the mandrel designing,the Wolter-Ⅰ X ray microscope ray tracing program is developed.According to the application requirements,the structure of Wolter-Ⅰ microscope is optimized.The influence of various design parameters on the final imaging performance is analyze.In terms of mandrel tolerance distribution,the mandrel surface figure error is classified combined with Legendre Fourier polynomial,and the imaging performance equations of initial figure error is deduced from geometric optics.2)The surface micro morphology after turning of NiP is studied.Combined with turning theory,the generation mechanism of NiP surface micro morphology is analyzed,and the relationship between surface micro morphology and turning parameters is established.Combined with the scattering theory,the relationship between the micro morphology of the turning surface and the surface diffraction is analyzed to select the appropriate turning parameters for turning.Finally,the microscope mandrel with a surface shape better than ±50 nm was obtained by using the in-situ measuring device.3)The polishing method of Wolter-Ⅰ mandrel is developed from the three-step process of plane-cylindrical-Wolter-Ⅰ mandrel.The semi-rigid mechanical polishing method is adopted to obtain ultra-smooth surface and ensure the accuracy of surface shape.The final polished surface roughness is RMS 0.66 nm at 120×120 μm region,RMS 0.23 nm at 5×5 μm region.CGH technology is used to measure the surface figure of the mandrel,and a new absolute detection method is developed to avoid the influence of the reference mirror figure of the interferometer.The final measurement results show that the surface shape is still controlled within ±50 nm.In this work,a fast and simple mandrel design and tolerance distribution method are discussed,and an effective mandrel fabricating process is explored,which lays a foundation for the fabrication of Wolter-Ⅰ microscope.