Hidekazu Takano

Development of full-field x-ray phase-tomographic microscope based on laboratory x-ray source

An X-ray phase tomographic microscope that can quantitatively measure the refractive index of a sample in three dimensions with a high spatial resolution was developed by installing a Lau interferometer consisting of an absorption grating and a π/2 phase grating into the optics of an X-ray microscope. The optics comprises a Cu rotating anode X-ray source, capillary condenser optics, and a Fresnel zone plate for the objective. The microscope has two optical modes: a large-field-of-view mode (field of view: 65 μm x 65 μm) and a high-resolution mode (spatial resolution: 50 nm). Optimizing the parameters of the interferometer yields a self-image of the phase grating with ~60% visibility. Through the normal fringe-scanning measurement, a twin phase image, which has an overlap of two phase image of opposite contrast with a shear distance much larger than system resolution, is generated. Although artifacts remain to some extent currently when a phase image is calculated from the twin phase image, this system can obtain high-spatial-resolution images resolving 50-nm structures. Phase tomography with this system has also been demonstrated using a phase object.

In-situ observation of polymer blend phase separation by x-ray Talbot-Lau interferometer

Talbot interferometer using white synchrotron radiation has been demonstrated for time-resolved X-ray phase imaging and tomography as well as four-dimensional phase tomography to observe dynamics in samples. In this study, X-ray phase tomography has been used to follow the time evolution of phase separation in polymer blend through heating treatment. For this purpose, we performed in-situ X-ray phase imaging and tomography with X-ray Talbot-Lau interferometer using white synchrotron radiation. The X-ray Talbot-Lau interferometer consisted of a source grating (30 μm in period), a π/2 phase grating (4.5 μm in period), an amplitude grating (5.3 μm in period) and a high-speed camera. A polymer blend sample of polystyrene (PS) (Mw = 76,500) and polymethyl methacrylate (PMMA) (Mw = 33,200) was used for the CT observation. A compound of the PS and PMMA was made by a twin-screw kneading extruder and put into an Al tube whose inner diameter was 6 mm. The sample temperature was maintained at desired temperature sequence by controlling a lamp for heating, and CT scans were repeated to track the changes in sample structures at a temporal resolution of 5 seconds. PS-rich phase and PMMA-rich phase changing with time evolution were revealed.

Comparison of image properties in full-field phase X-ray microscopes based on grating interferometry and Zernike's phase contrast optics

A grating interferometer (GI) system has been installed in an X-ray microscope equipped with a Zernike phase contrast (ZPC) system and a Cu rotating anode X-ray source. The GI and ZPC systems are switchable, and their performances of phase information extraction have been compared. The GI system is based on a Lau interferometer consisting of an absorption grating and a π/2 phase grating, which extracts a magnified phase shift map of a sample via a phase-stepping measurement. The ZPC system generates a phase contrast image by using a phase plate and a corresponding condenser device. The ZPC system and the GI system are compared in terms of detectability of phase objects. By the Fourier analysis of images of a logarithmic ruler pattern, the spatial resolution was found to be identical between the two systems. Although the sensitivity depends on the sample size, the signal-to-noise ratio of polystyrene spheres with a few microns in diameter was used for sensitivity comparison, showing the superior sensitivity of the GI system to that of the ZPC system. The quantitativeness of the GI system with the phase-stepping measurement was also demonstrated over the ZPC system, which generates halo and shade-off artifacts. The GI system exhibits twin image artifacts that need to be resolved for practical applications of the technique.A grating interferometer (GI) system has been installed in an X-ray microscope equipped with a Zernike phase contrast (ZPC) system and a Cu rotating anode X-ray source. The GI and ZPC systems are switchable, and their performances of phase information extraction have been compared. The GI system is based on a Lau interferometer consisting of an absorption grating and a π/2 phase grating, which extracts a magnified phase shift map of a sample via a phase-stepping measurement. The ZPC system generates a phase contrast image by using a phase plate and a corresponding condenser device. The ZPC system and the GI system are compared in terms of detectability of phase objects. By the Fourier analysis of images of a logarithmic ruler pattern, the spatial resolution was found to be identical between the two systems. Although the sensitivity depends on the sample size, the signal-to-noise ratio of polystyrene spheres with a few microns in diameter was used for sensitivity comparison, showing the superior sensitivit...

Development of grating-based x-ray phase tomography under the ERATO project

We have launched a project to promote grating-based X-ray phase imaging/tomography extensively. Here, two main activities are presented for enabling dynamic, or four-dimensional, X-ray phase tomography and nanoscopic X-ray phase tomography by grating interferometry. For the former, while some demonstrations in this direction were performed with white synchrotron radiation, improvement in image quality by spectrum tuning is described. A preliminary result by a total reflection mirror is presented, and as a next step, preparation of a 10% bandpass filter by a multilayer mirror is reported. For the latter, X-ray microscopes available both at synchrotron radiation facilities and laboratories equipped with a Fresnel zone plate are combined with grating interferometry. Here, a preliminary result with a combination of a Lau interferometer and a laboratory-based X-ray microscope is presented.