Tender Energy Spectroscopy Beamline at SSRF

This paper describes the design and performance of the tender energy spectroscopy beamline (BL16U1), a phase II beamline, at the Shanghai Synchrotron Radiation Facility. The beamline, based on an in-vacuum undulator source with 26 mm period , provides an operable energy range between 2.1 keV and 16 keV, covering the K edges of P to Rb and L3-edges of Zr to Bi. The principal optical elements of the beamline are a toroidal mirror, a liquid-nitrogen-cooled double-crystal monochromator, a high-harmonic-rejection mirror, and two pairs of Kirkpatrick–Baez (KB) mirrors. Three end-stations, including non-focusing, microprobe, and sub-microprobe types, are installed on the beamline. X-ray fluorescence (XRF) and X-ray absorption spectroscopy (XAS), including X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), are performed under vacuum or He atmosphere at the non-focusing end-station (with a beam spot size of ∼ 670 μm × 710 μm). Using two KB mirrors systems, micro-XRF (μXRF) mapping and micro-XANES (μXANES) studies can be performed with a spot size of approximately ∼ 3.3 μm × 1.3 μm at the microprobe end-station and with asmaller spot size of ∼ 0.5 μm×0.25 μm at the sub-microprobe end-station. The non-focusing end-station was officially opened to users in January 2024. The microprobe and sub-microprobe end-stations will be opened to users in the near future. This paper presents the characteristics, short-term technical developments, and early experimental results of this new beamline.