Abstract
Four-dimensional phase computed tomography (4D phase CT) by an X-ray Talbot interferometer (XTI) with white synchrotron radiation has ever been demonstrated at a temporal resolution of about 1 s for soft-matter samples. However, the radiation damage to samples caused by white synchrotron radiation occasionally hampers our understanding of the sample dynamical properties. Based on the fact that XTI functions with X-rays of a bandwidth up to ca. 10% with performance comparable to that by monochromatic X-rays, filtering white synchrotron radiation to generate a ‘pink-beam’ of a 10% bandwidth is effective to reduce radiation damage without degrading the image quality and temporal resolution. We have therefore developed pink-beam 4D phase CT at SPring-8, Japan by installing a multilayer mirror with a 10% bandwidth and a 25 keV central photon energy. XTI optimal at this photon energy was built downstream, and a CMOS-based X-ray detector was used to achieve fast image acquisitions with an exposure time of 1 ms (or 0.5 ms) per moiré image. The resultant temporal resolution of pink-beam 4D phase CT was 2 s (1 s). We applied the pink-beam 4D phase CT to in-situ observation of polypropylene, poly(methyl methacrylate), and polycarbonate under infrared laser irradiation (1064 nm). The dynamics of melting, bubbling, and ashing were successfully visualized in 3D movies without problematic radiation damage by synchrotron radiation.
Highlights
Computed tomography (CT) is an excellent non-destructive technique that maps X-ray absorption coefficient three-dimensionally in the case of X-ray absorption CT1 or X-ray refractive index in the case of X-ray phase CT2
The first action made in this study was to install a band-pass filtering multilayer mirror at BL28B2, SPring-8, Japan, where white synchrotron radiation from a bending section is available for various user experiments
A pink-beam was generated by a depthgraded W/Si multilayer mirror (Rigaku Innovative Technologies, Inc., USA), which functions as a band-pass filter against white synchrotron radiation impinging at a grazing angle of 5.11 mrad and generates a 10%-bandwidth X-rays with a 25-keV central photon energy, suppressing the second-order diffraction
Summary
Computed tomography (CT) is an excellent non-destructive technique that maps X-ray absorption (attenuation) coefficient three-dimensionally in the case of X-ray absorption CT1 or X-ray refractive index in the case of X-ray phase CT2. X-ray phase CT with white synchrotron radiation was performed for in vivo dynamical observations of living biological specimens[8], and the changes in inner structure of a living worm, which was considered to be respiratory tract, were visualized with a temporal resolution of 1 s. The first action made in this study was to install a band-pass filtering multilayer mirror at BL28B2, SPring-8, Japan, where white synchrotron radiation from a bending section is available for various user experiments. While a hard-X-ray Shack-Hartmann sensor was used for visualizing the laser ablation process in a projection mode[11], our system depicted melting, bubbling, and/or ashing induced by the laser in movies of 3D phase tomograms with a temporal resolution of 1 s or 0.5 s. We expect that valuable information would be obtained for the field of laser machining (ablation, drilling, cutting, trimming, welding, and so on), which could be used to design the appropriate laser ablation procedures for maintaining polymer strength[12,13,14]
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