Development of speckle-free channel-cut crystal optics using plasma chemical vaporization machining for coherent x-ray applications

We have developed a method of fabricating speckle-free channel-cut crystal optics with plasma chemical vaporization machining, an etching method using atmospheric-pressure plasma, for coherent X-ray applications. We investigated the etching characteristics to silicon crystals and achieved a small surface roughness of less than 1 nm rms at a removal depth of >10 μm, which satisfies the requirements for eliminating subsurface damage while suppressing diffuse scattering from rough surfaces. We applied this method for fabricating channel-cut Si(220) crystals for a hard X-ray split-and-delay optical system and confirmed that the crystals provided speckle-free reflection profiles under coherent X-ray illumination.Takashi Hirano, Taito Osaka, Yasuhisa Sano, Yuichi Inubushi, Satoshi Matsuyama, Kensuke Tono, Tetsuya Ishikawa, Makina Yabashi, and Kazuto Yamauchi, "Development of speckle-free channel-cut crystal optics using plasma chemical vaporization machining for coherent x-ray applications", Review of Scientific Instruments 87, 063118 (2016) https://doi.org/10.1063/1.4954731

Thin crystal development and applications for hard x-ray free-electron lasers

Taito Osaka, Makina Yabashi, Yasuhisa Sano, Kensuke Tono, Yuichi Inubushi, Takahiro Sato, Kanade Ogawa, Satoshi Matsuyama, Tetsuya Ishikawa, and Kazuto Yamauchi "Thin crystal development and applications for hard x-ray free-electron lasers", Proc. SPIE 8848, Advances in X-Ray/EUV Optics and Components VIII, 884804 (27 September 2013); https://doi.org/10.1117/12.2023465

Hard x-ray intensity autocorrelation using direct two-photon absorption

An intensity autocorrelation measurement is demonstrated to characterize a pulse duration of 9-keV x-ray free-electron laser (XFEL) pulses from a split-delay optical (SDO) system with four-bounce silicon 220 reflections in each branch. XFEL pulse replicas with variable time delays are generated by the SDO system itself. High intensity of >2×1016W/cm2 achieved in a self-seeding operation and careful data analysis allow the measurement with direct two-photon absorption. The autocorrelation trace gave a duration of 7.6±0.8fs in full width at half maximum for a Gaussian assumption. Furthermore, the trace shows good agreement with a simulation of the XFEL pulse shape propagating through the SDO system, irrespective of spectral chirps in the original XFEL pulses. Our results open the door toward direct temporal characterization of narrowband XFELs at the hard x-ray regime, such as self-seeded and future cavity-based XFELs, and indicate a solid way for temporal tailoring of ultrafast x-ray pulses with perfect crystals.Osaka T., Inoue I., Yamada J., et al. Hard x-ray intensity autocorrelation using direct two-photon absorption. Physical Review Research, 4, 1, L012035. https://doi.org/10.1103/PhysRevResearch.4.L012035

Crystal structure of CmABCB1 multi-drug exporter in lipidic mesophase revealed by LCP-SFX

がんの多剤排出の原因となっているABCトランスポーターの立体構造をSACLAのX線自由電子レーザーを用いて決定. 京都大学プレスリリース. 2021-12-23.CmABCB1 is a Cyanidioschyzon merolae homolog of human ABCB1, a well known ATP-binding cassette (ABC) transporter responsible for multi-drug resistance in various cancers. Three-dimensional structures of ABCB1 homologs have revealed the snapshots of inward- and outward-facing states of the transporters in action. However, sufficient information to establish the sequential movements of the open–close cycles of the alternating-access model is still lacking. Serial femtosecond crystallography (SFX) using X-ray free-electron lasers has proven its worth in determining novel structures and recording sequential conformational changes of proteins at room temperature, especially for medically important membrane proteins, but it has never been applied to ABC transporters. In this study, 7.7 mono­acyl­glycerol with cholesterol as the host lipid was used and obtained well diffracting microcrystals of the 130 kDa CmABCB1 dimer. Successful SFX experiments were performed by adjusting the viscosity of the crystal suspension of the sponge phase with hy­droxy­propyl methyl­cellulose and using the high-viscosity sample injector for data collection at the SACLA beamline. An outward-facing structure of CmABCB1 at a maximum resolution of 2.22 Å is reported, determined by SFX experiments with crystals formed in the lipidic cubic phase (LCP-SFX), which has never been applied to ABC transporters. In the type I crystal, CmABCB1 dimers interact with adjacent molecules via not only the nucleotide-binding domains but also the transmembrane domains (TMDs); such an interaction was not observed in the previous type II crystal. Although most parts of the structure are similar to those in the previous type II structure, the substrate-exit region of the TMD adopts a different configuration in the type I structure. This difference between the two types of structures reflects the flexibility of the substrate-exit region of CmABCB1, which might be essential for the smooth release of various substrates from the transporter

Damage to inorganic materials illuminated by focused beam of X-ray free-electron laser radiation

X-ray free-electron lasers (XFELs) that utilize intense and ultra-short pulse X-rays may damage optical elements. We investigated the damage fluence thresholds of optical materials by using an XFEL focusing beam that had a power density sufficient to induce ablation phenomena. The 1 μ4m focusing beams with 5.5 keV and/or 10 keV photon energies were produced at the XFEL facility SACLA (SPring-8 Angstrom Compact free electron LAser). Test samples were irradiated with the focusing beams under normal and/or grazing incidence conditions. The samples were uncoated Si, synthetic silica glass (SiO2), and metal (Rh, Pt)-coated substrates, which are often used as X-ray mirror materials.Takahisa Koyama, Hirokatsu Yumoto, Kensuke Tono, Tadashi Togashi, Yuichi Inubushi, Tetsuo Katayama, Jangwoo Kim, Satoshi Matsuyama, Makina Yabashi, Kazuto Yamauchi, and Haruhiko Ohashi "Damage to inorganic materials illuminated by focused beam of x-ray free-electron laser radiation", Proc. SPIE 9511, Damage to VUV, EUV, and X-ray Optics V, 951107 (12 May 2015); https://doi.org/10.1117/12.218277

Measurement of the X-ray spectrum of a free electron laser with a wide-range high-resolution single-shot spectrometer

We developed a single-shot X-ray spectrometer for wide-range high-resolution measurements of Self-Amplified Spontaneous Emission (SASE) X-ray Free Electron Laser (XFEL) pulses. The spectrometer consists of a multi-layer elliptical mirror for producing a large divergence of 22 mrad around 9070 eV and a silicon (553) analyzer crystal. We achieved a wide energy range of 55 eV with a fine spectral resolution of 80 meV, which enabled the observation of a whole SASE-XFEL spectrum with fully-resolved spike structures. We found that a SASE-XFEL pulse has around 60 longitudinal modes with a pulse duration of 7.7 ± 1.1 fs.Inubushi, Y.; Inoue, I.; Kim, J.; Nishihara, A.; Matsuyama, S.; Yumoto, H.; Koyama, T.; Tono, K.; Ohashi, H.; Yamauchi, K.; Yabashi, M. Measurement of the X-ray Spectrum of a Free Electron Laser with a Wide-Range High-Resolution Single-Shot Spectrometer. Appl. Sci. 2017, 7, 584. https://doi.org/10.3390/app7060584

Development of split-delay x-ray optics using Si(220) crystals at SACLA

Taito Osaka, Takashi Hirano, Makina Yabashi, Yasuhisa Sano, Kensuke Tono, Yuichi Inubushi, Takahiro Sato, Kanade Ogawa, Satoshi Matsuyama, Tetsuya Ishikawa, and Kazuto Yamauchi "Development of split-delay x-ray optics using Si(220) crystals at SACLA", Proc. SPIE 9210, X-Ray Free-Electron Lasers: Beam Diagnostics, Beamline Instrumentation, and Applications II, 921009 (8 October 2014); https://doi.org/10.1117/12.2060238