1. Status of Beamline BL07LSU at SPring-8
The University-of-Tokyo high-brilliance synchrotron soft X-ray outstation beamline
BL07LSU at SPring-8 has been maintained by the permanent staff members with adjuncts
for user operations. The scientific aim of the beamline is to promote advanced
spectroscopy for solid state and soft (including bio-) materials. There are three regular
endstations for ambient pressure X-ray photoelectron spectroscopy, 3D-scanningphotoelectron microscope (3D nano-ESCA) and high-resolution soft X-ray emission
spectroscopy (HORNET) that are open for users. There is also a free port station for users
who bring in their own experimental apparatus.
The beamline BL07LSU is equipped with a segmented cross-type undulator. Circularlyand linearly polarized soft X-rays can be used in user experiments at full energy range(250 – 2000 eV). By using phase shifters between the neighboring undulator segments,
polarization of the soft X-ray beam is regulated continuously and the switching frequency
can be tuned up to 13 Hz. At the end-stations, various scientific experiments were carriedout by both the laboratory staffs and users with applications of G-type (general), S-type(special), or P-type (priority). A user group of the S-type spends the long-term beamtime
to pursue the challenging issues in synchrotron radiation research. A user team of the Ptype proceeds an experiment mainly for developing technologies of beamline and endstation for the next generation light source.
It should be mentioned that the coronavirus (COVID-19) pandemic has continuously
been a serious issue in 2021. Safety and health of users at the beamline have been takencare during their beamtime experiment at the end-station.
Status of the individual end-stations are briefly described below.
(1) Ambient-pressure X-ray photoelectron spectroscopy (AP-XPS)
AP-XPS station is aimed mainly for operando observations of catalytic reactions at
the gas/solid interface. The AP-XPS system is equipped with a differentially pumped
electron analyzer (SPECS, PHOIBOS 150 NAP) and an ambient pressure gas cell. XPS
measurements can be performed both under ultrahigh vacuum and in near-ambient gas
pressure up to 100 mbar. Reactant and product molecules of a catalytic reaction aremonitored by mass spectrometer and, simultaneously, chemical states of the reaction
intermediates at a surface can be examined by AP-XPS.
In 2021, a variety of research projects was conducted at the AP-XPS station, forexample, operando observations of hydrogen permeations at metal alloys and of catalytic
reactions at model surfaces.

(2) 3D-scanning photoelectron microscope (3D-nanoESCA)
3D-nanoESCA can be used for sub-100 nm range microscopic 2D mapping and depth
profile of the chemical structure of functional materials and devices. In 2021, visible light
responsive Al-doped SrTiO3 photocatalytic particles and BaTaO2N photocatalytic
particles, developed by Prof. Hisatomi group at Shinshu University, were measured tocapture changes in band alignment by single-particle measurements. A core-level shiftreflecting the Fermi energy shift caused by a change in catalytic efficiency wassuccessfully monitored. As a demonstration study of the next-generation operando
spectromicroscopy system with a piezoelectric four-tip unit, the potential distribution of
single-layer CVD graphene on a p+-Si/SiO2 substrate was measured under an electric field
applied to the probe, where the probe was fixed to a sample holder. As a result, a clear
peak shift was detected only in the vicinity of the tip contact, suggesting a potential dropat the domain boundary.
(3) Ultra high-resolution soft X-ray emission spectroscopy (HORNET)
The station is dedicated for soft X-ray emission (or resonant inelastic X-ray scattering:RIXS) spectroscopy measurements with high-resolution (E/ΔE > 10,000) and undervarious environmental conditions (gas, liquid, and solid).
In the beginning of this term, new soft X-ray CCD detector with ultra-high spatialresolution (< 5mm) for next-generation synchrotron radiation (NanoTerasu) wasintroduced. Although the total resolution was only slightly improved due to the limited
beam size on the sample, it is expected that the resolution at NanoTerasu will beapproximately three times higher than the current improvement.
HORNET station was used for studies on temperature-dependent water hydrogen-bondbehavior in electrolyte membranes, spin polarization in half metals by RIXS-MCD,
demonstration of soft x-ray inelastic diffraction, CO2 sorption process in PDMS forsilicon materials. Two abroad applications (RIXS-MCD of CrX3 and dd excitation
observation of Fe-Co spinel materials) were conducted remotely. As part of the New
Academic Field Research, outstanding results were obtained in the study of a watermolecule confined in C60, and ionization of ultrafine water upon adsorption to hydrophilic
and hydrophobic surfaces.
(4) Soft X-ray imaging (Free-port station)
This year, we developed a new soft X-ray ptychography system at the free-port station.
The reflecting surface of the Wolter mirror, which was covered with Au, enables seamlessptychographic measurements in a wide energy range of soft X-rays at BL07LSU.
A soft X-ray ptychographic system with a total-reflection Wolter mirror achieved aresolution of approximately 50 nm in a test chart evaluation. We have also shown that it
is possible to visualize the microstructure of a mammalian cell over a wide photon energy
range without chromatic aberration. Furthermore, taking advantage of the long working
distance of the optical system, stereo imaging with a large rotation angle was also
attempted to measure the cell sample. Ptychographic imaging with a pink beam from theundulator was also possible.
The soft X-ray ptychography system based on the Wolter mirror optics is expected to behighly effective for investigating thick samples with complex three-dimensional
structures and chemical compositions.