Additional pinning effect by heavy-ion irradiation in coated conductors with artificial pinning centers

Sueyoshi, Tetsuro*; Ozaki, Toshinori*; Semboshi, Satoshi*; Sakane, Hitoshi*; Nishizaki, Terukazu*; Ishikawa, Norito

IEEE Transactions on Applied Superconductivity, 35(5), p.8000205_1 - 8000205_5, 2025/08

https://dx.doi.org/10.1109/TASC.2025.3527941

We investigated additional pinning effect on in-field Jc properties of coated conductors including YO nano-particles as artificial pinning centers (APCs), where three types of heavy-ion beams were employed. The addition of the irradiation defects enhanced the in-field Jc. Furthermore, more upward shift in the Jc was observed for the introduction of the defects with larger volume of the irradiation damage, not only in high magnetic fields but also in low magnetic fields. One factor of the irradiation effect is that the self-field Jc and the critical temperature (Tc) are relatively insensitive to the addition of the irradiation defects for the samples with APCs. Another is the glassy flux creep behavior over wide temperature region, suggesting that flux pinning by the combination of APCs and irradiation defects is strong against thermal fluctuation.

Near-infrared study of radiation damage in ion-irradiated cerium dioxide and cerium-gadolinium dioxide

Costantini, J.-M.*; Guillaumet, M.*; Lelong, G.*; Ishikawa, Norito; Seo, P.*; Yasuda, Kazuhiro*

Nuclear Instruments and Methods in Physics Research B, 558, p.165567_1 - 165567_6, 2025/01

https://doi.org/10.1016/j.nimb.2024.165567

Radiation damage is studied in ion-irradiated sintered CeO and (Ce, Gd)O samples. Near Infra-red (NIR) spectra measurements were carried out by using the diffuse reflectivity mode for all of these sintered samples. Samples were irradiated with 100-MeV Kr, 200-MeV Xe, and 36-MeV W ions. Four broad absorption bands centered at 3700, 4100, 6000, and 7600 cm (i.e. 0.46, 0.51, 0.74, and 0.94 eV) are deduced from fits of the FTIR spectra for the ion-irradiated CeO and (Ce, Gd)O samples accompanied by a change in color from ivory to green. No such bands are recorded for the virgin (Ce, Gd)O samples with 5, 10, and 15 mol GdO with an increasing amount of oxygen vacancies. Absorption bands are tentatively assigned to electronic transitions involving cerium vacancy levels in the band gap, which has been also observed under high-energy electron irradiation.

Application of EBSD as a method for analyzing irradiation damage in ceramics

Fujimura, Yuki; Ishikawa, Norito; Kondo, Keietsu

JAEA-Technology 2024-012, 26 Pages, 2024/10

JAEA-Technology-2024-012.pdf:3.03MB

While ceramic materials exhibit high temperature strength and corrosion resistance, they are also chemically stable. Specifically, aluminum oxide (AlO) is recognized as one of the highly radiation resistant materials. On the other hand, the precise evaluation of irradiation damage in these materials poses a significant challenge because detecting radiation damage induced in highly radiation-resistant ceramics is difficult. The objective of this study is to evaluate irradiation-induced lattice strain using Electron BackScatter Diffraction (EBSD), a technique commonly employed for damage analysis in metals. Ion irradiation tests were conducted on AlO, a representative highly radiation-resistant ceramic, at various doses. Through lattice strain analysis using EBSD, we successfully identified irradiation-induced lattice strain in the direction parallel to the irradiation, consistent with previous XRD analysis results. Lattice strain in the direction perpendicular to the irradiation was also detected. It was observed that the lattice strain tends to increase with increasing irradiation damage. In conclusion, lattice strain analysis using EBSD proves to be an effective method for assessing the irradiation effects on ceramics.

Development of standard substance for hydrogen analysis in materials

Ogawa, Hiroaki; Ishikawa, Norito

2023-Nendo Daigaku Kenkyu Josei Gijutsu Kenkyu Hokokusho, p.123 - 134, 2024/03

Evaluation of corrosion and hydrogen embrittlement is important in the quality control of stainless steel and the development of next steel materials assuming a high-pressure hydrogen environment. Typically, a secondary ion mass spectrometer (SIMS) is used to analyze hydrogen in steel materials. The hydrogen concentration of conventional standard substance for hydrogen analysis is as small as 1wt-ppm, which has been a problem in hydrogen analysis. We use a hydrogen-implant method to create a locally higher hydrogen concentration than that of the conventional. Hydrogen concentration analysis has been evaluated using the nuclear reaction analysis (NRA) method at a tandem accelerator. We have succeeded in creating a sample with a higher hydrogen concentration of about 1,900 wt-ppm than that of the conventional in locally.

Latent ion tracks were finally observed in diamond

Amekura, Hiroshi*; Chettah, A.*; Narumi, Kazumasa*; Chiba, Atsuya*; Hirano, Yoshimi*; Yamada, Keisuke*; Yamamoto, Shunya*; Leino, A. A.*; Djurabekova, F.*; Nordlund, K.*; et al.

Nature Communications (Internet), 15, p.1786_1 - 1786_10, 2024/02

https://doi.org/10.1038/s41467-024-45934-4

Injecting high-energy heavy ions in the electronic stopping regime into solids can create cylindrical damage zones called latent ion tracks. Although these tracks form in many materials, none have ever been observed in diamond, even when irradiated with high-energy GeV uranium ions. Here we report the first observation of ion track formation in diamond irradiated with 2-9 MeV C fullerene ions. Depending on the ion energy, the mean track length (diameter) changed from 17 (3.2) nm to 52 (7.1) nm. High resolution scanning transmission electron microscopy (HR-STEM) indicated the amorphization in the tracks, in which -bonding signal from graphite was detected by the electron energy loss spectroscopy (EELS).

Surface nanostructures on Nb-doped SrTiO irradiated with swift heavy ions at grazing incidence

Ishikawa, Norito; Fujimura, Yuki; Kondo, Keietsu; Szabo, G. L.*; Wilhelm, R. A.*; Ogawa, Hiroaki; Taguchi, Tomitsugu*

Nanotechnology, 33(23), p.235303_1 - 235303_10, 2022/06

https://doi.org/10.1088/1361-6528/ac58a5

A single crystal of SrTiO doped with niobium (Nb-STO) was irradiated with 200 MeV Au ions at grazing incidence. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) are used to study the relation between irradiation-induced change of surface topography and corresponding material property changes. As expected, multiple hillocks as high as 5-6 nm are imaged by AFM observation. It is also found that the region in between the adjacent hillocks is slightly elevated rather than depressed. Line-like contrasts along the ion paths are found in both AFM phase images and SEM images, indicating the formation of continuous ion tracks in addition to multiple hillocks. Cross-sectional transmission electron microscopy (TEM) observation shows that the ion tracks in the near-surface region are found to be relatively large, whereas buried ion tracks in the deeper region are relatively small. The results suggest that recrystallization plays an important role in the formation of small ion tracks in the deep region, whereas formation of large ion tracks in the near-surface region is likely due to the absence of recrystallization.

Nanopore formation in CeO single crystal by ion irradiation; A Molecular dynamics study

Sasajima, Yasushi*; Kaminaga, Ryuichi*; Ishikawa, Norito; Iwase, Akihiro*

Quantum Beam Science (Internet), 5(4), p.32_1 - 32_14, 2021/11

https://doi.org/10.3390/qubs5040032

The nano-pore formation process that occurs by supplying a thermal spike to single crystal CeO has been simulated using a molecular dynamics method. As the initial condition, high thermal energy was supplied to the atoms in a nano-cylinder placed at the center of a fluorite structure. A nano-pore was generated abruptly at around 0.3 ps after the irradiation. It grew to its maximum size at 0.5 ps, and successively it shrank during the time to 1.0 ps. The nano-pore size increased with increasing effective stopping power.

Summation of flux pinning by columnar defects tilted at different angles in YBCO thin films

Sueyoshi, Tetsuro*; Enokihata, Ryusei*; Yamaguchi, Hiroshi*; Fujiyoshi, Takanori*; Okuno, Yasuki*; Ishikawa, Norito

IEEE Transactions on Applied Superconductivity, 31(5), p.8000305_1 - 8000305_5, 2021/08

https://ieeexplore.ieee.org/document/9356111

Angular behaviors of critical current density Jc at 77 K, 1 T were investigated in YBCO films with columnar defects (CDs) tilted at small angles to the ab-plane before and after the additional introduction of CDs at different angles, where CDs were installed by heavy-ion irradiations. The enhanced Jc at by the initial irradiation at i=85 relative to the c-axis was reduced by the additional irradiation at i=75, whereas the Jc was increased at the intermediate angle between the two irradiation angles. The addition of CDs at i=0 also lowered the Jc around , which were enhanced by the initial irradiation angles of i=80.

Combined effect of flux pinning by three-directional columnar defects in a field-angular region of high- superconductors

Sueyoshi, Tetsuro*; Enokihata, Ryusei*; Hidaka, Yuka*; Irie, Masahiro*; Fujiyoshi, Takanori*; Okuno, Yasuki*; Ishikawa, Norito

Physica C, 582, p.1353824_1 - 1353824_5, 2021/03

https://doi.org/10.1016/j.physc.2021.1353824

We investigated the combined effect of flux pinning by three-directional columnar defects (CDs) in a wide field-angular range of YBaCuOy thin films, where CDs parallel to the -axis and CDs crossing at (=45, 60 and 80) relative to the c-axis were installed by 200 MeV Xe-ion irradiations. The three-directional CDs with 60 form a field angular curve of critical current density Jc with a broad peak centered at magnetic field (B) parallel to the -axis, whereas the Jc shows no peaks around the crossing angles of . When the crossing angle is expanded to =80, a drastic change in the field- angular behavior of Jc is induced: there is not a large enhancement of around B//c. We also demonstrated that the combined configuration consisting of CDs at = 0, 45, 60 and 80 provides a uniform enhancement of over a wide angular-region.

Comprehensive understanding of hillocks and ion tracks in ceramics irradiated with swift heavy ions

Ishikawa, Norito; Taguchi, Tomitsugu*; Ogawa, Hiroaki

Quantum Beam Science (Internet), 4(4), p.43_1 - 43_14, 2020/12

https://doi.org/10.3390/qubs4040043

Amorphizable ceramics were irradiated with 200 MeV Au ions, and the as-irradiated samples were observed by transmission electron microscopy (TEM). The ion track diameter and hillock diameter are similar for all the amorphizable ceramics. For SrTiO and niobium-doped STO, 200 MeV Au ion irradiation and TEM observation were also performed. The ion track diameters in these materials are found to be markedly smaller than the hillock diameters. The ion tracks in these materials exhibit inhomogeneity, which is similar to that reported for non-amorphizable ceramics. On the other hand, the hillocks appear to be amorphous, and the amorphous feature is in contrast to the crystalline feature of hillocks observed in non-amorphizable ceramics. No marked difference is recognized between the nanostructures in STO and those in Nb-STO.