Abstract: [Background] More than 80% of the protein in the protein database is solved by X-ray diffraction. The most commonly used wavelength is 0.0972 nm. Studies have shown that short-wavelength X-rays can reduce the radiation damage of crystals and improve the quality of X-ray diffraction data. [Purpose] In order to collect X-ray diffraction data from protein crystals with shorter wavelength at beamline BL17U in Shanghai Synchrotron Radiation Facility (SSRF), our first priority is to extend its energy range to 25 keV using compound refractive lens (CRL). [Methods] The flux rate and flux density of the CRL focused photon with different curvature radius of a single structure are calculated by introducing the acceptance rate R. The close contact type CRL and the interphase type CRL are also calculated. [Results] Focusing on the factors such as the focusing effect and the layout of the experimental station, we propose the best solution for focusing short-wavelength X-rays in BL17U. Using 31 lenses with a radius of 50 μm can obtain 3.2018×10¹⁴ s^-1·mm^-2 at 25 keV theoretically. [Conclusion] Through these theoretical calculation, we can prepare for collect protein crystal data using short X-ray wavelengths in BL17U.

Key words: Compound refractive lens, Synchrotron radiation, Photon flux density, Shorter wavelength X-ray