To realize achromatic full-field hard X-ray microscopy with a resolution better than 100 nm, we studied an imaging
system consisting of an elliptical mirror and a hyperbolic mirror. The figure accuracies of the elliptical and hyperbolic
mirrors required to obtain diffraction-limited resolution were investigated using a wave-optical simulator, and then
elliptical and hyperbolic mirrors were precisely fabricated, following the criterion of the figure accuracies. Experiments
to form a demagnified image of a one-dimensional slit installed 45 m upstream were conducted using the imaging system
at an X-ray energy of 11.5 keV at BL29XUL of SPring-8. The system could form a demagnified image with the best
resolution of 78 nm. In addition, the field of view to obtain a resolution better than 200 nm was 4.2 micron.
We present the development of a phase compensator for wavefront control of X-rays. The optical device is a 150 mm-long
total reflection mirror, the shape of which can be curved by adjusting the bias voltages of 36 piezoelectric ceramic
plates attached to the mirror. The mirror surface was smoothed and made flat by elastic emission machining. To achieve
a high degree of the accuracy in the controllability of a curved line, a Fizeau interferometer is placed in front of the
mirror surface to monitor its shape in the experiment. We will apply this device to the optical system for the realization
of sub-10-nm hard X-ray focusing.
We describe the fabrication of a long mirror for focusing X-ray free electron lasers to nanometer dimension, for the production of high photon density beams. The focusing mirror has an elliptical curved shape with a length of 400 mm and focal length of 550 mm. Electrolytic in-process dressing grinding is used for first-step figuring and elastic emission machining is employed for final figuring and surface smoothing. Figure accuracy with a peak-to-valley height of 2 nm is achieved. A focusing test was performed at BL29XUL of SPring-8 and found the focused beam size to be approximately
75 nm at 15 keV, very similar to the theoretical value.
Extremely high surface figure accuracy is required for hard x-ray nanofocusing mirrors to realize an ideal spherical
wavefront in a reflected x-ray beam. We performed the figure correction of an elliptically figured mirror by a differential
deposition technique on the basis of the wavefront phase error, which was calculated by a phase-retrieval method using
only intensity profile on the focal plane. The measurements of the intensity profiles were performed at the 1-km-long
beamline at SPring-8. The two measurements before and after the figure correction indicate that the beamwaist structure
around the focal point is greatly improved.
Nanofocused X-rays are indispensable because they can provide high spatial resolution and high sensitivity for X-ray
nanoscopy/spectroscopy. A focusing system with reflective optics is one of the most promising methods for producing
nanofocused X-rays due to its high efficiency and beams size. So, far we realize efficient hard X-ray focusing with a
beam size of 25nm. Our next project is realization of sub-10nm hard X-ray focusing. Here, we describe the design of
the graded multilayer mirror and evaluation method for hard X-ray focused beam.
We characterized beryllium foils and CVD diamond films/plates for synchrotron radiation beamline windows and x-ray
beam monitor especially in coherent x-ray applications. Sub-micron-resolution imaging with a zooming tube was
performed using spatially coherent x-rays at 1-km beamline 29XU of SPring-8. We found that the speckles observed in
the conventional powder and ingot beryllium foils were due to voids with diameter of several to ten-several microns. The
physical vapor deposition (PVD) eliminated the voids and the PVD beryllium showed the best performance with no
speckles. We characterized a commercially available polycrystalline CVD diamond window and CVD films as well as
beryllium foils. Polished thin diamond film showed rather uniform transmission image. We found dark spots at in-line
image due to Bragg diffraction from grains for thicker CVD diamond window.
We realized nearly diffraction-limited performance with a FWHM focal spot size of 25 nm at an x-ray energy of 15 keV at SPring-8. We explain performances of fabricated x-ray mirror, its fabrication technologies and future plan for realizing sub-10-nm focusing. We developed a novel method of at-wavelength metrology for evaluating the focusing hard x-ray beam in a grazing-incidence optical system. The metrology is based on the numerical retrieval method using the intensity distribution profile around the focal point. We demonstrated the at-wavelength metrology and estimated the surface figure error on a test mirror. An experiment for measuring the focusing intensity profile was performed at the 1-km-long beamline (BL29XUL) of SPring-8. The obtained results were compared with the profile measured by the optical interferometer and confirmed to be in good agreement with it. This technique has potential for characterizing wave-front aberration on elliptical mirrors for the sub-10-nm focusing.
Focusing methods using mirror optics are intensively studied in the field of X-ray microscopy because mirror optics has useful features such as high photon efficiency and no chromatic aberrations. Employing a wave-optical method, we investigated the relationship between the nature of figure errors on the mirror surface and optics performances. We also evaluated glancing angle sensitivity to focused beam and beamwaist stuructures. Obtained results showed unprecedented degrees of surface figure accuracy such as higher than 4 nm was required to realize nearly diffraction limited nanobeam. This simulation can also give important information for align KB mirrors setup.
We developed a high-spatial-resolution scanning X-ray fluorescence microscope (SXFM) with Kirkpatrick-Baez
mirrors. As a result of focusing tests at 15 keV, the focused beam having a FWHM of 30 x 50 nm2 was achieved.
Additionally, the size was controllable within the wide range of 30 ~ 1400 nm merely by adjusting the X-ray source
size. The observation of a fine test chart suggests that SXFM enables us to visualize the element distribution inside the
pattern at a spatial resolution better than 30 nm. We applied the SXFM to observe intracellular elemental distributions
at a single-cell level, so that we could acquire element distribution maps with a spatial resolution of sub-100 nm and
lower detection limit of 0.01 fg.
We have developed X-ray refraction based computed tomography (CT) which is able to visualize soft tissue in
between hard tissue. The experimental system consists of Si(220) diffraction double-crystals called the DEI (diffraction-enhanced
imaging) method, object locating in between them and a CCD camera to acquire data of 900 x-ray images.
The x-ray energy used was 17.5 keV. The algorithm used to reconstruct CT images has been invented by A.
Maksimenko et al.. We successfully visualized calcification and distribution of breast cancer nest which are the inner
structure. It has much higher contrast which in comparison with the conventional absorption based CT system.
We developed the computer-controlled figuring system having controllability of removal depths with nanometer accuracy and spatial resolutions close to 0.1mm. In this system, Elastic Emission Machining (EEM) using nozzle-type EEM head and Microstitching Interferometry (MSI) are employed as a machining method and a figure measurement method. In EEM, very small stationary spot profiles ware obtained, selecting small circle nozzle aperture of a 0.15 mm diameter. Surface figuring is performed with controlling scanning speeds of sample stages, so that a measured profile turned into designed one. MSI, which was developed on the basis of interferometric stitching technologies, has reproducibility at subnanometer level and with spatial resolution of 0.03 mm. In this study, we demonstrated computer controlled figuring, focusing on removal of high frequency figurer errors. Figure accuracy of 0.2 nm (RMS) was achieved in a cross-section profile with a length of 90mm.
X-ray focusing techniques using Kirkpatrick and Baez mirrors are promising due to their capability of highly efficient and energy-tunable focusing. We have been developing a hard-X-ray focusing system using K-B mirrors for an X-ray microscope. Here, we report the development of a mirror manipulator and focusing tests using the manipulator. Mirror alignment tolerances were estimated using two types of simulators: a ray-trace simulator and a wave-optical simulator. On the basis of the simulation results, the mirror manipulator was developed achieving optimum K-B mirrors setup. The focal size was achieved to be 48 x 36nm2 (V x H) in FWHM at 1km long beamline of SPring-8. The obtained spatial resolution test results indicate that a scanning microscope with the focused beam can resolve the line-and-space patterns of 80nm line width in a high visibility of 60%.
The stability of synchrotron beamline optics is required in experiments using x-ray coherence. Especially the stability of a monochromator is important in considering a high heat load due to exposure to intense polychromatic x-rays. We developed MOSTAB (monochromator stabilization) modules and carried out performance tests using SPring-8 beamlines. We succeeded in the simultaneous stabilization of the monochromatic x-ray beam intensity and position with MOSTAB. An attempt was also made to stabilize the x-ray beam at the 1 km experimental station at SPring-8.