Design And Application Of High Energy X-ray Compound Refractive Lens

Synchrotron radiation X-ray crystallography is the main method for determining the structure of biological macromolecules such as proteins.Most common wavelength currently used is 0.979 ?(12.662 keV).The X-ray diffraction intensity is proportional to the square of the wavelength,and the X-ray absorption cross-section in matter is proportional to the third power of the wavelength.This means that short-wavelength Xrays can increase the ratio of diffracted over absorbed,reduce the radiation damage of the crystal,and improve the quality of X-ray diffraction data.In order to research shortwavelength X-ray determine protein structure at beam-line BL17 U in Shanghai Synchrotron Radiation Facility(SSRF),it is necessary to expand its energy range first.Based on the principle of Compound Refractive Lens(CRL)focused X-ray,the parameters such as transmittance,effective aperture and gain of the compound refractive lens were analyzed.The properties of refraction coefficient ? and absorption coefficient ? of several commonly used X-ray materials are discussed for the compound refractive lens selection.The refractive index ? and the absorption coefficient ? are taken into account when choice suitable material for 25 keV energy X-ray.The flux and flux density of CRL focused photons with different radii of curvature for a single structure were calculated.The close contact type and interphase type of cascaded CRL were also calculated.Focusing on the factors such as the focusing effect and the layout of the laboratory,the best design scheme for focusing short wavelength X-rays on the BL17 U is proposed.According to the conditions of the optical device of the beam-line,the compound refraction lens is processed by the preliminary design scheme.The focusing experiment is done at the BL17 U,and the energy range of the beam-line can be extended to 20 keV and the diffraction data were collected by photons of 20 keV energy.The results of experimental data are consistent with the theory which proves that the short wavelength X ray can increase the ratio of diffracted over absorbed and improve the signal to noise ratio of protein crystal diffraction data this result can provide reference for beam-line upgrading in the future.