UVSOR is one of the highest-brilliance light sources in the extreme-ultraviolet region among the synchrotron radiation facilities with electron energies of less than 1 GeV. The low natural emittance of the UVSOR-III storage ring, 17.5 nm-rad, was accomplished after the successful completion of the storage ring upgrade project (the UVSOR-III project) in 2012. Eight bending magnets and six insertion devices are available as synchrotron light sources at UVSOR. There are a total of thirteen operational beamlines. Eleven of them are the so-called “Public beamlines”, which are open to scientists from universities and research institutes belonging to the government, public organizations, private enterprises and also those from foreign countries. The beamline BL6U is the “In-house beamlines”, and are dedicated to the use of research groups within Institute for Molecular Science (IMS). The beamline BL1U is a partially "Public" and partially "In-house" beamline. There is one tender X-ray (TX) station equipped with a double-crystal monochromator, six extreme ultraviolet (EUV) and soft X-ray (SX) stations with grazing incidence monochromators, three vacuum ultraviolet (VUV) stations with normal incidence monochromators, two infrared (IR) stations equipped with Fourier Transform interferometers, and one direct radiation station located after two tandem undulators, as shown in the appended table (next page) for all available beamlines at UVSOR in 2023. The details of the updates for undulator beamlines are the followings.
●In BL1U, the development of a new light source and the utilization of gamma-rays are being carried out. This beamline is equipped with a tandem undulators with a buncher section, which can be used for free electron laser in the range from visible to deep UV, VUV coherent harmonic generation, and generation of spatiotemporal structured light such as an optical vortex beam, a vector beam and double-pulsed wave packets.
It is also equipped with a femto-second laser system synchronized with the accelerator, which is used for the generation of Compton scattered gamma-rays. Users are provided with gamma-ray induced positron annihilation spectroscopy that can analyze nanometer-order defects in bulk materials. To increase the counting rate of annihilation gamma rays, an array detector with eight BaF2 scintillators was developed. The measurement can be completed in a few hours for metal samples.
●In BL3U, the ultrathin-liquid cell for low-energy XAS has been developed. The studies of local structures of several aqueous solutions and various chemical processes in solution such as catalytic and electrochemical reactions, and laminar flows in microfluidics by using operando XAS in C, N, and O K-edges were demonstrated. Moreover, an argon gas window that is effective from 60 to 240 eV with the removal of high-order X-rays, which will develop chemical research since it includes K-edges of Li and B and L-edges of Si, P, S, and Cl was established.
Resonant soft X-ray scattering (RSoXS) for soft materials is also applicable. RSoXS is similar to small angle X-ray scattering (SAXS) and can provide information on the mesoscopic structure (1-100 nm) of sample. This method has selectivity of elements, functional groups and molecular orientation. Since soft X-ray region include K-edge energies of light element (C, N, O), RSoXS is a powerful tool to investigate soft matters.
●BL4U, which is equipped with a scanning transmission soft X-ray microscope (STXM), is actively used not only by academic users but also by many industrial users. The STXM can be applied to wide range of sciences, such as polymer science, material science, cell biology, environmental science, and so on. In FY2020, it became possible to image the lithium K-edge with a spatial resolution of 72 nm. Final adjustments for the airtight sample transport system and the sample transport container were carried out for the organic substance analysis of the Hayabusa2 returned samples for the summer of FY2021.
●In BL5U, high energy resolution angle-resolved photoemission spectroscopy (ARPES) is available. Users can now use so-called “deflector mapping” for all kinetic energies and lens modes by using the latest version of ARPES analyzer. Users can also obtain spatial-dependence of the electronic structure of solid surfaces using micro-focused beam (50 μm). An alkali-metal deposition system has been installed. Potassium for example can be deposited while the sample is still mounted on the manipulator at low temperatures. As part of the development of spin-resolved ARPES, two-dimensional images of the spin-resolved spectrum of the Rashba splitting of Au(111) surface has been successfully obtained.
●At BL6U, one of the In-house beamlines, photoelectron momentum microscope (PMM), which is a new-concept multi-modal electronic structure analysis system with high resolution in real space and momentum space, has been installed and is in operation. A key feature of the PMM is that it can very effectively reduce radiation-induced damage by directly projecting a single photoelectron constant energy contour in reciprocal space with a radius of a few Å-1 or real space with a radius of a few hundred μm onto a 2D detector. Experiments such as valence band photoelectron spectroscopy on the micrometer scale and resonance photoelectron diffraction by soft X-ray excitation are performed. In FY2023, PMM's capabilities were further expanded by introducing an additional 2D spin filter. Two-dimensional images of the spin-resolved spectrum of the Rashba splitting of Au(111) surface has been also successfully obtained too following BL5U. In addition to grazing-incidence soft X-ray excitation, normal-incidence vacuum ultraviolet (VUV) beam with variable polarizations (horizontal/vertical) became also available at the same focal position of the PMM via a newly added branch from the next BL7U. This highly symmetrical measurement geometry completely eliminates the p-polarized linear dichroism effect in the circular dichroism measurements of valence band, making transition matrix element analysis much simpler and reliable.
●At BL7U, high-energy resolution ARPES is available with extremely low energy of photons (6 eV~) using the low-temperature 6-axis manipulator with a sample temperature 4.5-350 K. In FY2021, the deflector-type detector for the hemispherical analyzer was installed to realize an effective 2D measurement with the automated manipulator control. Users can perform the measurement of the bulk sensitive electronic structure of solids and the high-throughput measurement for molecular materials using high-photoionization cross-section using low-excitation photon energy.
Those wishing to use the open and in-house beamlines are recommended to contact the appropriate beamline contact persons (see next page). Applications can be submitted at NOUS (https:// nous.nins.jp/user/signin). All users are required to refer to the beamline manuals and the UVSOR guidebook, on the occasion of conducting the actual experimental procedures. For updated information on UVSOR, please see http://www. uvsor.ims.ac.jp.
UVSOR Synchrotron Facility, Institute for Molecular Science
Fumihiko MATSUI
