arXiv subjects

Takekazu Ishida

Publications and source records attributed to Takekazu Ishida.

10 recordsLinked to original sources

arXiv2025

Experimental Studies on Spatial Resolution of a Delay-Line Current-Biased Kinetic-Inductance Detector

A current-biased kinetic inductance detector (CB-KID) is a novel superconducting detector to construct a neutron transmission imaging system. The characteristics of a superconducting neutron detector have been systematically studied to improve spatial resolution of our CB-KID neutron detector. In this study, we investigated the distribution of spatial resolutions under different operating conditions and examined the homogeneity of spatial resolutions in the detector in detail. We used a commercial standard Gd Siemens-star pattern as a conventional method to estimate the spatial resolution, and a lab-made 10B-dot array intended to examine detailed profiles on a distribution of spatial resolutions. We found that discrepancy in propagation velocities in the detector affected the uniformity of the spatial resolutions in neutron imaging. We analyzed the ellipsoidal line profiles along the circumferences of several different test circles in the Siemens-star image to find a distribution of spatial resolutions. Note that we succeeded in controlling the detector temperature precisely enough to realize stable propagation velocities of the signals in the detector to achieve the best spatial resolution with a delay-line CB-KID technique.

physics.ins-det↗

arXiv2023

Orientation mapping of YbSn$_3$ single crystals based on Bragg-dip analysis using a delay-line superconducting sensor

Recent progress in high-power pulsed neutron sources has stimulated the development of the Bragg-dip and Bragg-edge analysis methods using a two-dimensional neutron detector with high temporal resolution to resolve the neutron energy by the time-of-flight method. The delay-line current-biased kinetic-inductance detector (CB-KID) is a two-dimensional superconducting sensor with a high temporal resolution and multi-hit capability. We demonstrate that the delay-line CB-KID with a $^{10}$B neutron conversion layer can be applied to high-spatial-resolution neutron transmission imaging and spectroscopy up to 100\,eV. Dip structures in the transmission spectrum induced by Bragg diffraction and nuclear resonance absorption in YbSn$_3$ single crystals. We successfully drew the orientation mapping of YbSn$_3$ crystals based on the analysis of observed Bragg-dip positions in the transmission spectrum.

physics.app-ph↗

arXiv2021

High Spatial Resolution Neutron Transmission Imaging Using a Superconducting Two-Dimensional Detector

Neutron imaging is one of the most powerful tools for nondestructive inspection owing to the unique characteristics of neutron beams, such as high permeability for many heavy metals, high sensitivity for certain light elements, and isotope selectivity owing to a specific nuclear reaction between an isotope and neutrons. In this study, we employed a superconducting detector, current-biased kinetic-inductance detector (CB-KID) for neutron imaging using a pulsed neutron source. We employed the delay-line method, and high spatial resolution imaging with only four reading channels was achieved. We also performed wavelength-resolved neutron imaging by the time-of-flight method for the pulsed neutron source. We obtained the neutron transmission images of a Gd-Al alloy sample, inside which single crystals of GdAl3 were grown, using the delay-line CB-KID. Single crystals were well imaged, in both shapes and distributions, throughout the Al-Gd alloy. We identified Gd nuclei via neutron transmissions that exhibited characteristic suppression above the neutron wavelength of 0.03 nm. In addition, the ^{155}Gd resonance dip, a dip structure of the transmission caused by the nuclear reaction between an isotope and neutrons, was observed even when the number of events was summed over a limited area of 15 X 12 um^2. Gd selective imaging was performed using the resonance dip of ^{155}Gd, and it showed clear Gd distribution even with a limited neutron wavelength range of 1 pm.

physics.app-ph↗

arXiv2021

Practical tests of neutron transmission imaging with a superconducting kinetic-inductance sensor

Samples were examined using a superconducting (Nb) neutron imaging system employing a delay-line technique which in previous studies was shown to have high spatial resolution. We found excellent correspondence between neutron transmission and scanning electron microscope (SEM) images of Gd islands with sizes between 15 and 130 micrometer which were thermally-sprayed onto a Si substrate. Neutron transmission images could be used to identify tiny voids in a thermally-sprayed continuous Gd2O3 film on a Si substrate which could not be seen in SEM images. We also found that neutron transmission images revealed pattern formations, mosaic features and co-existing dendritic phases in Wood's metal samples with constituent elements Bi, Pb, Sn and Cd. These results demonstrate the merits of the current-biased kinetic inductance detector (CB-KID) system for practical studies in materials science. Moreover, we found that operating the detector at a more optimal temperature (7.9 K) appreciably improved the effective detection efficiency when compared to previous studies conducted at 4 K. This is because the effective size of hot-spots in the superconducting meanderline planes increases with temperature, which makes particle detections more likely.

cond-mat.supr-con↗

arXiv2020

Homogeneity of neutron transmission imaging over a large sensitive area with a four-channel superconducting detector

We previously proposed a method to detect neutrons by using a current-biased kinetic inductance detector (CB-KID), where neutrons are converted into charged particles using a 10B conversion layer. The charged particles are detected based on local changes in kinetic inductance of X and Y superconducting meanderlines under a modest DC bias current. The system uses a delay-line method to locate the positions of neutron-10B reactions by acquiring the four arrival timestamps of signals that propagate from hot spots created by a passing charged particle to the end electrodes of the meanderlines. Unlike conventional multi-pixel imaging systems, the CB-KID system performs high spatial resolution imaging over a 15 mm x 15 mm sensitive area using only four channel readouts. Given the large sensitive area, it is important to check the spatial homogeneity and linearity of detected neutron positions when imaging with CB-KID. To this end we imaged a pattern of 10B dot absorbers with a precise dot pitch to investigate the spatial homogeneity of the detector. We confirmed the spatial homogeneity of detected dot positions based on the distribution of measured dot pitches across the sensitive area of the detector. We demonstrate potential applications of the system by taking a clear transmission image of tiny metallic screws and nuts and a ladybug. The image was useful for characterizing the ladybug noninvasively. Detection efficiencies were low when the detector was operated at 4 K, so we plan to explore raising the operating temperature towards the critical temperature of the detector as a means to improve counting rates.

physics.ins-det↗

arXiv2019

Monte Carlo Radiation Transport Modelling of the Current-Biased Kinetic Inductance Detector

Radiation transport simulations were used to analyse neutron imaging with the current-biased kinetic inductance detector (CB-KID). The PHITS Monte Carlo code was applied for simulating neutron, $^{4}$He, $^{7}$Li, photon and electron transport, $^{10}$B(n,$α$)$^{7}$Li reactions, and energy deposition by particles within CB-KID. Slight blurring in simulated CB-KID images originated $^{4}$He and $^{7}$Li ions spreading out in random directions from the $^{10}$B conversion layer in the detector prior to causing signals in the $X$ and $Y$ superconducting Nb nanowire meander lines. 478 keV prompt gamma rays emitted by $^{7}$Li nuclei from neutron-$^{10}$B reactions had negligible contribution to the simulated CB-KID images. Simulated neutron images of $^{10}$B dot arrays indicate that sub 10 $μ$m resolution imaging should be feasible with the current CB-KID design. The effect of the geometrical structure of CB-KID on the intrinsic detection efficiency was calculated from the simulations. An analytical equation was then developed to approximate this contribution to the detection efficiency. Detection efficiencies calculated in this study are upper bounds for the reality as the effects of detector temperature, the bias current, signal processing and dead-time losses were not taken into account. The modelling strategies employed in this study could be used to evaluate modifications to the CB-KID design prior to actual fabrication and testing, conveying a time and cost saving.

physics.ins-det↗

arXiv2019

Energy-resolved neutron imaging with high spatial resolution using a superconducting delay-line kinetic inductance detector

Neutron imaging is one of the key technologies for non-destructive transmission testing. Recent progress in the development of intensive neutron sources allows us to perform energy-resolved neutron imaging with high spatial resolution. Substantial efforts have been devoted to developing a high spatial and temporal resolution neutron imager. We have been developing a neutron imager aiming at conducting high spatial and temporal resolution imaging based on a delay-line neutron detector, called the current-biased kinetic-inductance detector, with a conversion layer $^{10}$B. The detector allowed us to obtain a neutron transmission image with four signal readout lines. Herein, we expanded the sensor active area, and improved the spatial resolution of the detector. We examined the capability of high spatial resolution neutron imaging over the sensor active area of 15 $\times$ 15 mm$^2$ for various samples, including biological and metal ones. We also demonstrated an energy-resolved neutron image in which stainless-steel specimens were discriminating of other specimens with the aid of the Bragg edge transmission.

physics.app-ph↗

arXiv2011

Torque Theory of Anisotropic Superconductors with No Phenomenological Parameter in determining Vortex Core Size

The contribution of vortex core has been taken into account properly in constructing a torque theory for multiband superconductors. We employ the prescription of describing internal magnetic field in the vortex lattice by Hao {\it et al.} and by Yaouanc {\it et al.} to derive a torque formula as a natural extension of a preceding London theory. In marked contrast with the preceding model, our novel formula does not contain a phenomenological parameter $η$, which prevents us from obtaining a {\it true} upper critical field $H_{\rm c2}$ by analyzing an experimental torque curve. The parameter $η$ was originally introduced to take care of the uncertainty in determining the vortex core size $ξ_v$. Furthermore, we reveal that the $η$ value is universally scaled by anisotropy $γ$, magnetic field $B$, and $H_{\rm c2}$ due to field dependence of $ξ_v$. This may revitalize the single-band Kogan model in combination with a universal function $η(γ, B, H_{\rm c2})$ instead of a constant $η$.

cond-mat.supr-con↗

arXiv2003

Ginzburg-Landau calculations of d-wave superconducting dot in s-wave superconducting matrix

We have developed a numerical method that calculated superconducting states and magnetic field distributions for the composite structures of the High-Tc superconductor and the conventional superconductor in arbitrary geometries. We show spontaneous magnetic flux appears at the corner of the boundary of these two superconductors. Also we propose High-Tc superconducting dot embedded in conventional superconductors, which is named as d-dot and show the spatial distribution of superconducting order parameters and the magnetic field.

cond-mat.supr-con↗

arXiv2002

Superconducting anisotropy and evidence for intrinsic pinning in single crystalline MgB$_2$

We examine the superconducting anisotropy $γ_c = (m_c / m_{ab})^{1/2}$ of a metallic high-$T_c$ superconductor MgB$_2$ by measuring the magnetic torque of a single crystal. The anisotropy $γ_c$ does not depend sensitively on the applied magnetic field at 10 K. We obtain the anisotropy parameter $γ_c = 4.31 \pm 0.14$. The torque curve shows the sharp hysteresis peak when the field is applied parallel to the boron layers. This comes from the intrinsic pinning and is experimental evidence for the occurrence of superconductivity in the boron layers.

cond-mat.supr-con↗