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 μm 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.
X-ray free electron lasers (XFELs) with intense and ultra-short pulse X-rays possibly induce damage to optical elements.
We investigated the damage thresholds of optical materials by using focusing XFEL beams with sufficient power density
for studying ablation phenomena. 1-μm focusing beams with 10 keV photon energy were produced at the XFEL facility
SACLA (SPring-8 Angstrom Compact free electron LAser). The focusing beams irradiated samples of rhodium-coated
substrate, which is used in X-ray mirror optics, under grazing incident condition.
We evaluated the irradiation damage induced to platinum/carbon multilayers induced by hard X-ray free-electron lasers
(XFELs). In this study, in order to test the use of the platinum/carbon multilayers for future XFEL focusing applications,
we evaluated the structures in almost exactly the condition in which they would actually be used. The X-ray reflectivity of
the multilayers was measured by using XFELs, and a cross-section of the multilayer that was irradiated by an XFEL was
observed by transmission electron microscopy. We used a non-monochromatic beam at a photon energy of 10 keV. We
confirmed that the intensity of the conditions under which the multilayers are to be used is sufficiently lower than the
breakdown threshold of platinum/carbon multilayers.
We investigated a one-dimensional Wolter mirror (which consists of an elliptical mirror and a hyperbolic mirror) with
the aim of developing an achromatic full-field X-ray microscope with a resolution of better than 50 nm. X-ray mirrors
were ultraprecisely fabricated by elastic emission machining to give a figure accuracy of 2 nm (peak-to-valley). A one-dimensional
Wolter mirror that had been precisely constructed was evaluated in terms of the point-spread function at the
center of the field of view (FOV) and the FOV at an X-ray energy of 11.5 keV at BL29XUL of SPring-8. It was found to
have a minimum resolution of 43 nm and a FOV equivalent to 12.1 μm. These results are highly consistent with