Kentaro Uesugi

Construction and Commissioning of A 248 m‐long Beamline with X‐ray Undulator Light Source

A medium‐length beamline with undulator source, BL20XU at SPring‐8, was constructed, and opened to public use. The distance from source point to the end of the beamline is 248 m. By utilizing the long beam transport path, the beamline has advantages for experiment that requires high spatial coherence in hard X‐ray regions.

Zernike phase-contrast x-ray microscope with pseudo-Kohler illumination generated by sectored (polygon) condenser plate

Zernike phase contrast x-ray microscope has been developed at the undulator beamline 20XU and 47XU of SPring-8. The system consists of a pseudo-Kohler-illuminating system, a Fresnel zone plate objective with outermost zone width of 100 nm, a Zernike phase plate (0.96-μm-thick tantalum, λ/4 or 3λ/4 phase-shifter at 8 keV) installed at the back-focal plane of the objective, and a visible-light conversion type cooled CCD camera as an image detector. A sectored (polygon) condenser plate is employed as the condenser in order to secure a large and flat field of view. Details and experimental results of the system will be shown.

Development of fast (sub‐minute) micro‐tomography

An x‐ray fast micro‐tomography system was developed at medical and imaging beamline BL20B2 in SPring‐8. We attempted a “continuous rotation method” whereby the sample keeps rotating in the beam during the measurement. The image acquisitions are synchronized with the trigger pulses branched from the stepper motor controller. An electron multiplier (EM)‐CCD camera (C9100‐02, 1000×1000 pixels, 30 fps, 8 μm/pixel, Hamamatsu Photonics) and beam‐monitor AA40P (Hamamatsu Photonics) were used as an image detector. The effective pixel size of the detector was 4.9 μm/pixel and the spatial resolution was about 15 μm. The total measurement time for 900 projections has been reduced to 36 s. The reconstruction time was also reduced using GPGPU and SSD system. Using these techniques, preliminary experiment for 4‐D (time resolved 3‐D) micro‐imaging has also been performed.

PSF measurement of imaging detectors with an x-ray microbeam

Point spread functions (PSF) of some kinds of x-ray imaging detectors are directly measured using x-ray microbeam. The experiment has been performed at bending magnet beamline BL20B2 and undulator beamline BL2oXU of Spring-9. The microbeam is focused using a Fresnel zone plate (FZP) with coherent illumination to 0.3micrometers (almost outermost zone width of the FZP). The imaging detectors are put at the focal plane and directly detect the microbeam. Two types of high spatial resolving detectors are tested. One is x-ray- electron conversion type with electro-magnetic lens, and spatial resolution is estimated to 0.7micrometers . The other is x-ray-visible light conversion type with optical lens and the spatial resolution is estimated to 1.0micrometers .

Hard X-ray Imaging Microscopy using X-ray Guide Tube as Beam Condenser for Field Illumination

An optical system for illumination of object in x-ray imaging microscopy is developed. The optical system is a beam condenser consisting of a single-bounce conical-shape mono-capillary (x-ray guide tube: XGT) made of Pyrex glass. The XGT condenser was tested at the beam line 47XU of SPring-8 using a Fresnel zone plate as an objective lens. Comparing with the microscope without beam condenser, the flux density is improved by a factor of 12–20 in the x-ray energy range of 6–8 keV. Test patterns with a 50 nm-structure are clearly resolved at 8 keV with an exposure time less than 1 s.

Direct Measurement of the Resolving Power of X‐ray CT System in SPring‐8

Resolving power of high spatial resolution X‐ray computed tomography (CT) system was evaluated by taking CT images of artificial test patterns at BL47XU in SPring‐8 (SP‐μCT BL47XU). The system consists of an in‐vacuum type undulator, a double crystal monochromator cooled with liquid nitrogen, a high precision sample stages and a high spatial resolution X‐ray detector. For the precise measurement of the resolving power, the artificial test patterns of Cu/Al concentric multilayer were fabricated by DC sputtering deposition at AIST Kansai. 7 or 5 layers of Cu/Al are deposited by period of 2 μm and 1 μm. Therefore the resolving power could be measured at 4 μm and 2 μm with each test pattern. It was confirmed that the system had a resolving power of 2 μm at 15keV from the CT images of test patterns. The resolution is not independent on the used energy. At 30keV, the resolving power was slightly poorer than 2 μm. The result was consistent with the point spread functions of the high resolution detector measured ...

Investigation of Imaging Properties of Mouse Eyes Using X‐ray Phase Contrast Tomography

The structure of a whole eye of mouse was studied with an X‐ray Talbot grating interferometer. The distribution of crystallin concentration in the lens was quantitatively measured by X‐ray phase contrast tomography. A new technique to measure the crystallin concentration in the lens is proposed. By using the proposed method, the gradient of crystallin concentration in the lens was estimated. A ray‐trace of a mouse whole eye was performed with the refractive indices derived from the crystallin concentration.

Optimization of X-ray phase contrast imaging system toward high-sensitivity measurements of biological organs

X-ray phase contrast imaging and tomography using a Talbot grating interferometer is currently available for user experiments at BL20B2 in SPring-8. The measurement condition for X-ray phase contrast tomography has been optimized to achieve high-sensitivity measurements of biological soft tissues and organs. Some biological samples were measured to demonstrate the high-sensitivity imaging.

Differential Phase‐Contrast Scanning X‐Ray Microscope For Observation Of Low‐Z element Specimen

Differential phase‐contrast scanning x‐ray microscope/microtomography have been developed. A fast readout charge‐coupled device (CCD) camera coupled with a visible‐light conversion unit is used as a detector to record the transmitted intensity distribution of far‐field image for every pixel in a scan. Simultaneous absorption and phase‐contrast images are given from a single scan by image‐processing of the CCD frames. The system is constructed at BL20XU of SPring‐8, and its feasibility is demonstrated at the photon energy of 8 keV. A tantalum test chart is observed and its finest structure of 140 nm pitch pattern is clearly observed. Measured phase sensitivity is approximately λ/270. Some low‐Z element specimens are observed and obtained phase contrast image shows much higher sensitivity than that of absorption contrast.

CMOS Imaging Detectors as X-ray Detectors for Synchrotron Radiation Experiments

CMOS imagers are matrix‐addressed photodiode arrays, which have been utilized in devices such as commercially available digital cameras. The pixel size of CMOS imagers is usually larger than that of CCD and smaller than that of TFT, giving them a unique position. Although CMOS x‐ray imaging devices have already become commercially available, they have not been used as an x‐ray area detector in synchrotron radiation experiments. We tested performance of a CMOS detector from Rad‐icon (Shad‐o‐Box1024) in medical imaging, small‐angle scattering, and protein crystallography experiments. It has pixels of 0.048 mm square, read‐out time of 0.45 sec, 12‐bit ADC, and requires a frame grabber for image acquisition. The detection area is 5‐cm square. It uses a Kodak Min‐R scintillator screen as a phosphor. The sensitivity to x‐rays with an energy less than 15 keV was low because of the thick window materials. Since the readout noise is high, the dynamic range is limited to 2000. The biggest advantages of this detecto...