Advances in Engineering Advances in Engineering features breaking research judged by Advances in Engineering advisory team to be of key importance in the Engineering field. Papers are selected from over 10,000 published each week from most peer reviewed journals.
Significance
X-ray imaging is a coherent lensless imaging technique that can produce a high-resolution image of a given sample. Current research trends demand the visualization of internal microstructures non-destructively. Moreover, with the growing interest in dynamical phenomena in various fields of fundamental and industrial sciences, demand for accessing internal structures of objects with high spatial and temporal resolutions has significantly grown. Consequently, high-speed X-ray imaging has advanced significantly over the past decades. This has been largely due to the availability of high-brilliance synchrotron radiation (SR) sources and X-ray free-electron lasers. Unfortunately, for 3D imaging of non-repeatable phenomena, the temporal resolution becomes worse since the depth resolved visualization requires a rotation of the sample. In particular, past publications have shown that a 3D tomographic reconstruction requires a few hundred projection images, and eventually the temporal resolution would be as low as sub-second. A conceptually simple approach to the faster data acquisition is to increase the speed of sample rotation. However, such a high-speed rotation is incompatible with a sample that is affected by the centrifugal force arising from the rotation, e.g. living beings and fluids.
Alternatively, the X-ray multi-beam technique which can illuminate a sample from multiple directions simultaneously, provides a promising approach to the high-speed 4D tomography. In fact, recent publications have reported on a detector system that has a flexible branched optical fiber bundle, which was capable of simultaneous recording four projection images on a single CMOS camera. Remarkably, the reported system realized a spatially flexible detection of the multiple beams; however, the resulting spatial resolution was as low as 200 μm. On this account, researchers from the Tohoku University, Japan: Dr. Liang Xiaouyu and Professor Wataru Yashiro, in collaboration with Dr. Tetsuroh Shirasawa at the National Institute of Advanced Industrial Science and Technology, Professors Wolfgang Voegeli, and Etsuo Arakawa at the Tokyo Gakugei University and Dr. Kentaro Kajiwara at Japan Synchrotron Radiation Research Institute (JASRI) developed a high-speed multi-beam X-ray imaging using a detector system and the recently developed multi-beam X-ray optics by Voegeli et al. Their work is currently published in the research journal, Applied Physics Express.
In their approach, the research team used a component of the multi-beam X-ray optics, which consisted of eight Si (001) single-crystalline blades aligned on a hyperbolic plane. Each of the blades diffracted X-rays by the (110) lattice planes and illuminated the sample, placed at the focus of the hyperbola, from a different angle. Based on their setup, the X-ray beams passing through the sample were incident on the scintillator screens and the fluorescence were transferred through the relay lenses (magnification of 1) and mirrors to a CMOS camera.
The authors found that by utilizing the optical relay lenses and mirrors for connecting four scintillator screens to a CMOS camera, they successfully obtained nine projection images of a sample at once with an exposure time of 0.5ms, without moving the sample, X-ray source, and detector. In fact, to demonstrate the potential of the high-speed and high-spatial-resolution 4D X-ray tomography, the team captured the dynamical behaviors of a light-bulb filament and a living ladybug with a temporal resolution of 0.5ms.
In summary, the study successfully demonstrated a detector system which realized the multi-beam X-ray imaging with a higher spatial resolution. In other words, the authors performed a high-speed multi-beam X-ray imaging by using a detector system and the multi-beam X-ray optics. The results were remarkable and in good agreement with literature. In a statement to Advances in Engineering, Professor Wataru Yashiro said that their detector system can be potentially extended to capture all the ∼30 beams, distributed in an angular range of about ±70°, to realize the high-speed 4D tomography.
Reference
Tetsuroh Shirasawa, Liang Xiaouyu, Wolfgang Voegeli, Etsuo Arakawa, Kentaro Kajiwara, Wataru Yashiro. High-speed multi-beam X-ray imaging using a lens coupling detector system. Applied Physics Express: volume 13, 077002 (2020).
