Research On The Shape Of Elliptical Focusing Mirror Based On Double-drive Four-point Roller Bending Device

The superior performance of synchrotron radiation led to the comprehensive development of bending technology in beamline optics.Since elliptical optical elements can improve the focusing ability of beamlines,obtaining high-precision elliptical surfaces by means of bending has formed the development trend of large-sized optical elements in focusing scenarios.On the basis of mechanical bending,a dual-drive fourpoint roller bending mechanism that can achieve unequal torque output is designed.,Compared with the U-shaped bending mechanism,the clamping force has less influence and the surface shape accuracy is high.Combined with material mechanics,finite element analysis,nano-radian long-range surface profiler test and other means,the influence of gravity load on elliptical bending mirror is explored to obtain highprecision elliptical bending surface shape that meets the needs of beamline use.The main research contents are as follows:(1)Taking the mirror with the size of 1200mm×70mm×50mm(length×width×height)as the research object,based on the requirements of the object distance of 26.5m,the image distance of 13 m and the grazing incidence angle of 2.8mrad,according to the theoretical ellipsoid equation and The beam deformation moment equation is used to calculate the unequal moment applied to both ends of the bending mirror,and the error of the ellipse theoretical bending surface is 0.013?rad.Analyze and calculate the residual surface shape residual error of multi-point compensation of the bending mirror under the influence of gravity,and calculate the minimum surface shape residual error of single-point to four-point drive compensation with the torque compensation method.The result is reduced from 0.707?rad to 0.049?rad.In principle It is demonstrated that multi-point drive compensation can gradually reduce the influence of gravity load.(2)In order to verify the influence of gravity load on the accuracy of the bending mirror surface,the finite element analysis software ANSYS workbench is used to simulate and drive the dual-drive four-point roller bending mechanism,and the ellipse is obtained under the influence of gravity and gravity respectively Bending results are0.058?rad,1.858?rad.In this paper,it is verified by simulation analysis that the influence of gravity on the surface shape of the bending mirror cannot be reduced by means of torque compensation,and a combination of multi-point drive compensation and torque compensation is adopted,and the residual error of simulation compensation obtained by adjustment is reduced from 0.822?rad to 0.06?rad.The calculation process of the theoretical multi-point compensation is verified.At the same time,by increasing the driving torque of the elliptical surface shape,the slope errors of the optimal elliptical simulation surface shape corresponding to multi-point compensation are 0.81?rad,0.25?rad,0.105?rad,and 0.075?rad,respectively.The elliptical bending moment has a downward trend with the increase of the number of compensation points.(3)Based on the surface measurement method of the actual bending mirror,the test principle and experimental environment of the nano-radian long-range surface shape meter are introduced.The best compression and bending result of the elliptical shape under the influence of gravity is 2.38?rad by means of torque compensation.Due to the large error,the multi-point compensation method of first compensation and then bending is used to debug the driving displacement of the elliptical shape.Test the surface shape results of single-point to four-point compensation,and then drive the displacement to test the corresponding elliptical bending surface shape error.The final results are 1.257?rad,0.656?rad,0.548?rad,and 0.519?rad.The experimental results are consistent with the trend of simulation bending results,which verifies the analysis process of elliptical bending under the influence of gravity compensation.Finally,the index detection of the bending mechanism is carried out,and the sensitivity,repeatability and stability are all within the acceptable range.In this paper,the specific influence of the multi-point compensation trend of gravity load on the shape of the elliptical bending surface is studied through the doubledrive four-point roller mechanism,which has reference significance in the related work of improving the accuracy of the elliptical bending surface.