Status of RIXS Beamline BL02U at NanoTerasu

Abstract The construction of the resonant inelastic X-ray scattering (RIXS) beamline BL02U at NanoTerasu was completed in March 2024, with commissioning starting in April 2024. BL02U is a dedicated beamline designed for ultrahigh-resolution RIXS, specifically optimized for a “2D-RIXS spectrometer” utilizing dispersive X-rays. The beamline features a varied-line-spacing plane grating monochromator with entrance slits. The monochromator disperses the incident X-rays by energy, and the sample is directly irradiated with the dispersive X-rays by placing it at the focal point. The 2D-RIXS spectrometer not only resolves the energy of the scattered X-rays but also images the spatial distribution of the incident X-rays using a 1D imaging function. By the beamline commissioning, we evaluated the focusing properties, the resolution performance of the monochromator, and the photon flux at the sample. The results showed that the focusing properties and photon flux were in excellent agreement with the design specifications. The resolving power of the beamline monochromator could not be accurately determined, since it far exceeded the limitations of measurement technique using X-ray absorption spectra of N 2 gas. However, preliminary spectrometer commissioning confirmed that the combined resolving power of the beamline and spectrometer has reached the world’s highest level. This directly implies that the beamline itself also possesses world-class energy resolution. These results demonstrate the exceptional performance of the BL02U beamline. The challenging final goals will be pursued through continued commissioning of both the beamline and spectrometer.