X-ray focusing to 62 keV by compound refractive lenses for high-pressure x-ray diffraction

This study describes high-energy x-ray focusing optics using compound refractive lenses (CRLs) for high-pressure x-ray diffraction (XRD) with a monochromatic x-ray beam. A CRL-based x-ray transfocator was upgraded and installed in the optics hutch at the BL10XU beamline of SPring-8. The instrument can be equipped with two types of CRLs in parallel: a newly designed aluminum (Al) CRL for x-ray energies of 40-62 keV and an existing glassy carbon CRL for those up to 40 keV. In only the Al-CRL-based x-ray transfocator, a 62 keV monochromatic x-ray beam with horizontal (H) and vertical (V) focused spots, whose sizes were 189 and 10.5 µm, respectively, and a flux of 1.32 × 10¹¹ phs/s were generated. A polymer SU-8 CRL fabricated via deep x-ray lithography was installed to further reduce the x-ray beam size. The Al-CRL and the SU-8 CRL were combined to generate a smaller spot size of 12.5 (H) × 11.0 (V) μm² with a flux of 3 × 10¹⁰ phs/s at 62 keV. A two-step optical configuration combining an x-ray transfocator and SU-8 CRL provides a valuable method for high-pressure XRD using a high-energy x-ray focused beam. The optical design and performance of the Al-CRL-based x-ray transfocator, its combination with the SU-8 CRL, and the first results of the focusing optics commissioning are presented here.