arXiv subjects

Takaki Hatsui

Publications and source records attributed to Takaki Hatsui.

9 recordsLinked to original sources

arXiv2026

Assessment of the Imaging Performance of the CITIUS High-Resolution Detector for Heavy Charged Particles and Neutrons

We report on the assessment of the imaging performance of CITIUS -- a high-speed X-ray detector developed for the large-scale synchrotron radiation facility SPring-8-II -- for heavy charged particles and neutrons. To characterize the detector response, an irradiation experiment was performed using alpha particles from an $^{241}$Am source at four back-bias voltages of 400V, 300 V, 200 V, and 170 V, thereby controlling the amount of charge diffusion. A Geant4 model of the experiment was constructed, and four model parameters were determined by template fitting to the measured signal cluster shape distributions. The best-fit values are: an intrinsic energy spread of 5% for the source, a gold fraction of 0.4 for the Au-Pd coating, a lateral charge diffusion spread of 26.5 $μ$m over a drift distance of 650 $μ$m at 400V back-bias, and a per-pixel readout noise of 10000 $e^{-}$ in the medium-gain channel. Using the obtained sensor model, simulations were performed for 4 MeV alpha particles and cold neutrons to evaluate the expected spatial resolution. In both cases, simulated CITIUS, when operated in a gain-selecting mode between high and medium gains, yields a substantial improvement: at a pixel size of 70 $μ$m for example, the resolution improves from 9.1 $μ$m to 1.2 $μ$m for alpha particles, and from 26 $μ$m to 1.9 $μ$m for cold neutrons. These results suggest that two key features of CITIUS -- its gain-selecting architecture and the substantial charge sharing enabled by the long carrier drift distance -- extend its imaging capabilities beyond X-rays to heavy charged particles and neutrons.

physics.ins-det↗

arXiv2026

Probing keV mass QCD axions with the SACLA X-ray free electron laser

Axions are hypothetical particles, proposed to account for the invariance of CP symmetry in quantum chromodynamics. While axions and axion-like-particles are well-motivated by string theory and beyond-Standard-Model extensions, they have remained elusive to experimental searches even after significant effort over many decades. Building on a recent development using an X-ray free electron laser to search for cosmologically favoured axions of mass $m_{a} \lesssim 0.01$ eV, we extend previous bounds on the ALP-photon coupling, $g_{aγγ}$, by over an order of magnitude. We exploit the Bormann effect of Laue crystals in a light-shining-through-wall experiment, with broad sensitivity to $m_a \lesssim$ 22 eV. Moreover for $m_{a} \in$ (3460, 3480) eV our sensitivity reaches down to the QCD axion coupling prediction, providing the most stringent laboratory constraints in this mass range.

hep-ph↗

arXiv2026

ROIX-Comp: Optimizing X-ray Computed Tomography Imaging Strategy for Data Reduction and Reconstruction

In high-performance computing (HPC) environments, particularly in synchrotron radiation facilities, vast amounts of X-ray images are generated. Processing large-scale X-ray Computed Tomography (X-CT) datasets presents significant computational and storage challenges due to their high dimensionality and data volume. Traditional approaches often require extensive storage capacity and high transmission bandwidth, limiting real-time processing capabilities and workflow efficiency. To address these constraints, we introduce a region-of-interest (ROI)-driven extraction framework (ROIX-Comp) that intelligently compresses X-CT data by identifying and retaining only essential features. Our work reduces data volume while preserving critical information for downstream processing tasks. At pre-processing stage, we utilize error-bounded quantization to reduce the amount of data to be processed and therefore improve computational efficiencies. At the compression stage, our methodology combines object extraction with multiple state-of-the-art lossless and lossy compressors, resulting in significantly improved compression ratios. We evaluated this framework against seven X-CT datasets and observed a relative compression ratio improvement of 12.34x compared to the standard compression.

eess.IV↗

arXiv2025

Paradigm Shift in Infrastructure Inspection Technology: Leveraging High-performance Imaging and Advanced AI Analytics to Inspect Road Infrastructure

Effective road infrastructure management is crucial for modern society. Traditional manual inspection techniques remain constrained by cost, efficiency, and scalability, while camera and laser imaging methods fail to capture subsurface defects critical for long-term structural integrity. This paper introduces ROVAI, an end-to-end framework that integrates high-resolution X-ray computed tomography imaging and advanced AI-driven analytics, aiming to transform road infrastructure inspection technologies. By leveraging the computational power of world-leading supercomputers, Fugaku and Frontier, and SoTA synchrotron facility (Spring-8), ROVAI enables scalable and high-throughput processing of massive 3D tomographic datasets. Our approach overcomes key challenges, such as the high memory requirements of vision models, the lack of labeled training data, and storage I/O bottlenecks. This seamless integration of imaging and AI analytics facilitates automated defect detection, material composition analysis, and lifespan prediction. Experimental results demonstrate the effectiveness of ROVAI in real-world scenarios, setting a new standard for intelligent, data-driven infrastructure management.

cs.DC↗

arXiv2017

Single-Shot 3D Diffractive Imaging of Core-Shell Nanoparticles with Elemental Specificity

We report 3D coherent diffractive imaging of Au/Pd core-shell nanoparticles with 6 nm resolution on 5-6 femtosecond timescales. We measured single-shot diffraction patterns of core-shell nanoparticles using very intense and short x-ray free electron laser pulses. By taking advantage of the curvature of the Ewald sphere and the symmetry of the nanoparticle, we reconstructed the 3D electron density of 34 core-shell structures from single-shot diffraction patterns. We determined the size of the Au core and the thickness of the Pd shell to be 65.0 +/- 1.0 nm and 4.0 +/- 0.5 nm, respectively, and identified the 3D elemental distribution inside the nanoparticles with an accuracy better than 2%. We anticipate this method can be used for quantitative 3D imaging of symmetrical nanostructures and virus particles.

physics.ins-det↗

arXiv2015

Compensation for TID Damage in SOI Pixel Devices

We are investigating adaption of SOI pixel devices for future high energy physic(HEP) experiments. The pixel sensors are required to be operational in very severe radiation environment. Most challenging issue in the adoption is the TID (total ionizing dose) damage where holes trapped in oxide layers affect the operation of nearby transistors. We have introduced a second SOI layer - SOI2 beneath the BOX (Buried OXide) layer - in order to compensate for the TID effect by applying a negative voltage to this electrode to cancel the effect caused by accumulated positive holes. In this paper, the TID effects caused by Co gamma-ray irradiation are presented based on the transistor characteristics measurements. The irradiation was carried out in various biasing conditions to investigate hole accumulation dependence on the potential configurations. We also compare the data with samples irradiated with X-ray. Since we observed a fair agreement between the two irradiation datasets, the TID effects have been investigated in a wide dose range from 100~Gy to 2~MGy.

physics.ins-det↗

arXiv2015

X-ray Radiation Hardness of Fully-Depleted SOI MOSFETs and Its Improvement

X-ray radiation hardness of FD-SOI n- and p-MOSFET has been investigated. After 1.4 kGy(Si) irradiation, 15% drain current increase for n-MOSFET and 20% drain current decrease for p-MOSFET are observed. From analysis of gmmax-Vsub, the major cause of n-MOSFET drain current change is the generated positive charge in BOX. On the other hand, the major cause of p-MOSFET drain current change is the radiation induced gate channel modulation by the generated positive charge in sidewall spacer. It is confirmed that the p-MOSFET drain current change is improved by higher PLDD dose. Thinner BOX is also proposed for further radiation hardness improvement.

physics.ins-det↗

arXiv2014

Development and Performance of Kyoto's X-ray Astronomical SOI pixel (SOIPIX) sensor

We have been developing monolithic active pixel sensors, known as Kyoto's X-ray SOIPIXs, based on the CMOS SOI (silicon-on-insulator) technology for next-generation X-ray astronomy satellites. The event trigger output function implemented in each pixel offers microsecond time resolution and enables reduction of the non-X-ray background that dominates the high X-ray energy band above 5--10 keV. A fully depleted SOI with a thick depletion layer and back illumination offers wide band coverage of 0.3--40 keV. Here, we report recent progress in the X-ray SOIPIX development. In this study, we achieved an energy resolution of 300~eV (FWHM) at 6~keV and a read-out noise of 33~e- (rms) in the frame readout mode, which allows us to clearly resolve Mn-K$α$ and K$β$. Moreover, we produced a fully depleted layer with a thickness of $500~{\rm μm}$. The event-driven readout mode has already been successfully demonstrated.

astro-ph.IM↗

arXiv2013

Single-shot 3D structure determination of nanocrystals with femtosecond X-ray free electron laser pulses

Coherent diffraction imaging (CDI) using synchrotron radiation, X-ray free electron lasers (X-FELs), high harmonic generation, soft X-ray lasers, and optical lasers has found broad applications across several disciplines. An active research direction in CDI is to determine the structure of single particles with intense, femtosecond X-FEL pulses based on diffraction-before-destruction scheme. However, single-shot 3D structure determination has not been experimentally realized yet. Here we report the first experimental demonstration of single-shot 3D structure determination of individual nanocrystals using ~10 femtosecond X-FEL pulses. Coherent diffraction patterns are collected from high-index-faceted nanocrystals, each struck by a single X-FEL pulse. Taking advantage of the symmetry of the nanocrystal, we reconstruct the 3D structure of each nanocrystal from a single-shot diffraction pattern at ~5.5 nm resolution. As symmetry exists in many nanocrystals and virus particles, this method can be applied to 3D structure studies of such particles at nanometer resolution on femtosecond time scales.

physics.optics↗