Design Of X-ray Kinoform Progressive Focusing Refraction Lens

In this paper,the X-ray refraction lens,a collimating,focusing and used for synchrotron radiation facility,is systematically studied.In order to obtain smaller focusing spot,Kinoform progressive focusing refraction lens design for X-ray was proposed.The nano-focusing performance of adiabatically designed Cartesian oval refocusing lenses is compared with other well known compound refractive lenses with parabolic profile（both simple concave and kinoform types）.Using Beam Propagation Method（BPM）simulation,it is shown that our design based on ideal cartesian oval lenses（OVAL）does significantly improve the focusing properties compared to other parabolic lens based designs,e.g.adabatic focusing lenses（AFL）,which doesn’t take into account of the refocusing effect.This points to the importance of optimizing complex lens design in improving nano-focusing lens performance.The main research results of this paper are as follows:1.The simulation of X-ray beam propagation is realized by programming language.The simulation program can effectively obtain the propagation of X-ray beam in the lens and free space,which provides the basis for finding the lens with the best focusing performance.2.The focusing characteristics of long Kinoform lens（LKL）andshort Kinoform lens（SKL）are systematically compared.SKL has diffraction and refraction properties at the same time,so in addition to the position of its main focus,there are also several secondary focal points.However,SKL is less affected by edge diffraction effect,so it is superior to LKL in efficiency and focal length.However,LKL has only one focus,which is a huge advantage over SKL;The wavefront distortion can be reduced by changing the shape design of the lens,thereby obtaining smaller focusing size and higher intensity gain.3.The focusing characteristics of X-ray Kinoform progressive focusing refraction lens are systematically studied.The focusing characteristics are analyzed by using compound refraction lens（CRL）.The results show that Kinoform is more suitable for collimation than focusing.In order to obtain better focusing performance,a parabolic adiabatic focusing lens was designed.The simulation results show that a 100 micron LKL AFL with Si as the lens material can focus the X-ray with a photon energy of 20 ke V,and obtain a focal spot of 24.42 nm（FWHM）with an intensity gain of more than 320.In order to further explore the focusing performance of the refraction lens,the ideal lens surface is designed based on the cubic X-ray approximate solution of ideal Cartesian equation,the aperture,lens material and X-ray photon energy areunchanged,and Kinoform lens aperture and beam transverse size matching design.Ideal Cartesian Oval refocusing Kinoform refraction lens（LKL OVAL）is designed.The simulation results show that the lens achieves 13.56 nm（FWHM）focal spot and 700 times peak gain.It provides a feasible design method for improving the focusing performance of nano-focusing refractive lens.