Noriyuki Igarashi

We report the development and initial applications of the multi-functional research and development beamlines BL-11A and BL-11B at the Photon Factory, which are designed to enable simultaneous use of hard and soft x-rays. The two beamlines share a common bending-magnet source and deliver independently monochromatized hard- and soft-x-ray beams that can be focused onto the same sample position in a downstream experimental hutch, providing a versatile platform for two-beam experiments in which hard and soft x-rays can serve as pump and/or probe beams in various combinations. As proof-of-concept demonstrations, we performed probe–probe measurements of water electrolysis on a cobalt electrocatalyst and pump–probe measurements of x-ray-induced dissociation of a caged compound. In the probe–probe scheme, hard- and soft-x-ray absorption spectroscopy was carried out simultaneously to track correlated changes in the catalyst oxidation state and oxygen-related intermediates during the oxygen evolution reaction. In the pump–probe scheme, chemical changes in 2-iodosobenzoic acid induced by hard-x-ray excitation at the iodine L3 edge were monitored using soft-x-ray absorption spectroscopy at the oxygen K edge.

The energy-switchable storage ring (ESSR) is proposed as a light source that achieves high-brilliance synchrotron radiation across a wide wavelength range, from vacuum ultraviolet to hard X-rays, and efficient power consumption. The ESSR facilitates the effective operation of large-scale systems required for large experimental apparatus and stringent safety management. It also significantly improves research quality by enabling a more precise understanding of sample states, particularly subtle differences in experimental conditions that are difficult to reproduce fully.

An X-ray analyzer-based optics with a zoom function is proposed for observing various samples with apparent-absorption contrast, phase contrast and scattering contrast. The proposed X-ray optics consists of a collimator crystal and an analyzer crystal arranged in a nondispersive (+, −) geometry with a sample placed between them. For the implementation of the zoom function, an asymmetrically cut crystal in the rotated-inclined geometry was used for the analyzer. Proof-of-principle experiments were performed at the vertical wiggler beamline BL-14B of the Photon Factory. First, the magnification was set to 1×, and then it was zoomed into the optimal magnification (10×). At these magnifications, tri-modal contrast cross-sectional images of a sample were obtained by computed tomography. It was confirmed that the image quality at 10× was superior to that at 1×. This achievement opens up new possibilities for observing an entire sample or regions of interest within a sample at optimal magnification, and is expected to be useful for materials science, condensed matter physics, archeology and biomedical science.

We propose a variable-magnification full-field x-ray microscope using two Fresnel zone plates (FZPs). By moving the positions of the two FZPs, the magnification can be continuously changed even if the sample and camera positions are fixed. It was demonstrated that the magnification can be changed in the range of 25–150× using a hard x-ray beam at 14.4 keV. Using the first FZP as a convex lens and the second FZP as a concave lens, high magnification can be achieved at a short camera length. Even under the condition of a camera length of about 7 m, a magnification higher than 300× was achieved, and a line and space pattern with a pitch of 40 nm was observed at 10 keV. By inserting a knife edge at an appropriate position in the optical system, a phase-contrast image can be easily obtained, which is useful for soft-tissue observation of biological samples.

The Hybrid Ring with a superconducting-linac injector as a highly flexible synchrotron radiation source to enable new experimental techniques and enhance many existing ones is proposed. It is designed to be operated with the coexistence of the storage (SR) bunches characterized by the performance of the storage ring, and the single-pass (SP) bunches characterized by the performance of the superconducting linac. Unique experiments can be performed by simultaneous use of the SR and SP beams, in addition to research with various experimental techniques utilizing the versatile SR beam and research in the field of ultrafast dynamics utilizing the ultrashort pulse of the SP beam. The extendability of the Hybrid Ring will allow it to be developed into a synchrotron radiation complex.

The nucleating effect of silk fibroin nano-disc (SFN) on the crystallization behavior of poly(L-lactic acid) (PLLA) was investigated by simultaneous synchrotron small- and wide-angle X-ray scattering measurements. For the isothermal crystallization at 110 °C from the melt, the induction period of the PLLA specimens containing 1% SFN was reduced compared to that of the neat specimens, indicating the acceleration of the nucleation of PLLA. The final degree of crystallinity was also increased, and the crystallization half-time was decreased, which indicates that the overall crystallization process was accelerated. Furthermore, the final value of the crystallite size (the lateral size of the crystalline lamella) was slightly lower for the specimens containing 1% SFN than that for the PLLA neat specimen, although the crystallites started growing much earlier. However, it was found that there was no effect of SFN on the growth rate of the crystallite size. The lamellar thickening process was also accelerated with a clear overshooting phenomenon with the inclusion of 1% SFN. As for the polymorphism, the α’ phase is dominant with about 96%, but a small amount of the α phase (4%) is found to exist. It was found that the SFN can also accelerate the formation of the minor α phase as well as the major α’ phase.

At the Photon Factory, we operate three SAXS beamlines: BL-6A, BL-10C, and BL-15A2. BL-15A2 is an undulator beamline, which has characteristic features in the tender X-ray region from 2100 to 4000 eV. In the BL-15A2 experimental hutch, two diffractometers are placed in tandem, and the upstream one is specially designed for tender X-ray scattering experiments. In particular, tender X-ray GISAXS is a very powerful tool for analyzing the depth-dependent surface structure of thin films and functional membranes. The diffractometer is equipped with an in-vacuum sample chamber and vacuum-compatible hybrid pixel array detector, PILATUS3 2M, which is directly connected to the beamline duct. The configuration allows high S/N scattering data to be obtained in the tender X-ray region. To improve the performance, we upgraded the beamline vacuum system, added a gate valve with an internal interlock, developed the sample heating system for in-situ tender X-ray GISAXS experiments, and enhanced the graphical user interface with an automated sample alignment function. These improvements have shortened the sample exchange time from over 1 hour to about 10 minutes as well as realized safer operations in a more user-friendly experimental environment.

By using wide-angle X-ray scattering (WAXS), small-angle neutron scattering, and theoretical scattering function simulation, we have clarified the effect of glycerol on both the thermal structure transition and the hydration-shell of myoglobin. At the glycerol concentration, ≤ ∼40 % v/v, the decreasing tendency in the maximum dimension and the radius of gyration was observed by X-ray scattering. The neutron scattering result using the inverse contrast variation method directly shows the preservation of the hydration-shell density at the concentration ≤ ∼40 % v/v. This phenomenon is reasonably explained by the preferential exclusion of glycerol from the protein surface to preserve the hydration shell, as suggested by the previous studies. While, at the concentration, ≥ 50 % v/v, the opposite tendency was observed. It suggests the preferential solvation (partial preferential penetration or replacement of glycerol into or with hydration-shell water surrounding the protein surface) occurs at the higher concentration. The observed WAXS scattering data covers the distinct hierarchical structural levels of myoglobin structure ranging from the tertiary structure to the secondary one. Therefore, we have clarified the effect of glycerol on the thermal structural stability myoglobin at different hierarchical structural levels separately. Against the temperature rise, the structural transition temperatures for all hierarchical structural levels were elevated. Especially, the tertiary structure of myoglobin was more stabilized compared with the internal-structure and the helix-to-cross transition. It suggests that the protective action of glycerol on protein structures essentially results from the preservation of the preferential hydration-shell of proteins.

BL-15A is a new x-ray undulator beamline at the Photon Factory. It will be dedicated to two independent research activities, simultaneous XAFS/XRF/XRD experiments, and SAXS/WAXS/GI-SAXS studies. In order to supply a choice of micro-focus, low-divergence and collimated beams, a double surface bimorph mirror was recently developed. To achieve further mirror surface optimization, the pencil beam scanning method was applied for “in-situ” beam inspection and the Inverse Matrix method was used for determination of optimal voltages on the piezoelectric actuators. The corrected beam profiles at every focal spot gave good agreement with the theoretical values and the resultant beam performance is promising for both techniques. Quick and stable switching between highly focused and intense collimated beams was established using this new mirror with the simple motorized stages.