National Institute for Fusion Science

Multivariate analysis of X-ray absorption and Raman spectra from samples prepared by a high-throughput melting system was conducted to investigate the effects of ZrO 2 concentration ( x ) on the Zr coordination environment and the glass network structure in ZrO 2 -doped R 2 O–CaO–SiO 2 glasses ( R = Na, K). The hundreds of samples were synthesized using a slurry-based combinatorial method involving Pt-Au microwells, followed by measurements of their Zr K-edge X-ray absorption near-edge structure and Raman spectra. Principal component analysis and non-negative matrix factorization revealed distinct structural evolution depending on the alkali species. For R = K , at x < 5 mol%, Zr predominantly adopted a highly symmetric six-coordinated environment. The spectral analysis suggests that this environment is stabilized by preferential charge compensation by Ca 2+ ions. This regime showed an increase in Q 3 (Zr) units without Q 2 formation. As x increased, the results indicate that K + ions participated in charge compensation, reducing Zr site symmetry and promoting Q 2 formation. Consequently, only tetragonal ZrO 2 precipitated at x > 13 mol%. In contrast, for R = Na, a less symmetric Zr environment and the simultaneous formation of Q 2 and Q 3 (Zr) units were observed across all concentrations, implying mixed charge compensation by Na + and Ca 2+ ions. These structural differences led to the precipitation of both monoclinic and tetragonal ZrO 2 phases at x > 16 mol%. The results demonstrate that the competition between network modifiers for charge compensation governs the glass structure and crystallization behavior.

This paper presents an AC inductive energization method for evaluating high-temperature superconducting (HTS) assembled conductors cooled by liquid hydrogen. A short-circuited secondary coil composed of REBCO wires was fabricated and tested under liquid-nitrogen and liquid-hydrogen environments. In liquid-nitrogen cooling, phase shifts and waveform distortions in the Rogowski-coil voltage were observed when the secondary current approached the conductor's critical current (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IC</i>), demonstrating that voltage signals can serve as reliable indicators of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IC</i> Under liquid-hydrogen cooling, secondary currents up to 4985 A were achieved before the power supply shut down because of overvoltage protection. These results establish AC inductive energization as a safe, non-destructive diagnostic method for HTS conductors and highlight the potential of liquid hydrogen for next-generation large-scale superconducting devices

This study reviews experimental observations of parity transitions in the mode structures of magnetohydrodynamic (MHD) instabilities in magnetically confined plasmas. The transition between even and odd-parity modes, which is closely related to changes in the topology of a magnetic vessel, suggests the formation and healing of the magnetic island. While the transitions from even to odd parity have been reported in several tokamak devices, recent experiments in the Large Helical Device (LHD) have revealed conventional even-to-odd parity transitions due to various instabilities and a novel transition from odd to even parity. These include transitions associated with energetic ion-driven resistive interchange instabilities, locked-mode-like instabilities, ”Edge” MHD instabilities, and double-odd-parity modes. These findings highlight the need for advanced diagnostics and theoretical modeling to further clarify the mechanisms governing parity transitions.

Slower oxidative fibers are more resistant to eccentric contraction (ECC)‐induced muscle damage than fast‐twitch glycolytic fibers, but the mechanisms remain unclear. This study investigated the roles of the exercise‐inducible PGC‐1α isoform PGC‐1α‐b and utrophin in protecting against ECC‐induced damage. ECCs were induced by supramaximal electrical stimulation of the left triceps surae in C57BL/6N wild‐type (WT), PGC‐1α‐b transgenic (Tg), utrophin knockout (Utrn KO), and PGC‐1α‐b Tg/Utrn KO mice. Although the proportion of fast‐type myosin heavy chain (MyHC) IIb in the gastrocnemius muscle was modestly lower in PGC‐1α‐b Tg and PGC‐1α‐b Tg/Utrn KO mice than in WT and Utrn KO mice, MyHC IIb remained the predominant isoform. At 3 days post injury (dpi), WT and Utrn KO mice exhibited reduced maximum isometric torque (MIT), Evans blue dye (EBD) staining in MyHC IIb‐positive fibers, and calpain‐1 activation. In contrast, PGC‐1α‐b Tg and PGC‐1α‐b Tg/Utrn KO mice showed substantial MIT recovery at 1 dpi and minimal EBD uptake and calpain‐1 activation at 3 dpi. PGC‐1α‐b Tg muscles also preserved excitation‐contraction coupling proteins and displayed increased mitochondrial markers and integrin α7B expression. Together, our findings suggest that PGC‐1α‐b confers resistance to ECC‐induced muscle damage through a Utrn‐independent mechanism.

Abstract The plasma transport analysis code TRANSP and full-orbit following code LORBIT were used to study fast-ion loss in the Experimental Advanced Superconducting Tokamak (EAST) under varying discharge parameters and heating scenarios, considering the synergistic effect of neutral beam injection (NBI) and ion cyclotron range of frequency (ICRF). To more faithfully simulate fast ion loss processes, the axisymmetric two dimensional poloidal contours of the EAST first wall and the antenna limiters were used as the loss boundary and then stretched toroidally to construct a three dimensional boundary structure. Results indicate that the fast ion loss diminishes as the plasma current (IP) and toroidal magnetic field (Bt) increase. Furthermore, the impact of different magnetic configurations on the fast-ion loss was considered. Increasing the distance between the antenna and the separatrix (R gapout ) can significantly reduced the fast-ion loss. When the toroidal magnetic field was reversed, .i.e., B t &gt; 0, the lower single-null configuration was more effective in mitigating the fast-ion loss than double-null and upper single-null configurations. A significant reduction in the fraction of fast-ion loss was observed when an outer strike point was positioned on the vertical target plate. Finally, the effects of varying NBI energies, injection angles, and ICRF antenna phases were investigated. The results indicate that, within certain limits, fast-ion loss decreases as the NBI injection angle increases, whereas higher NBI injection energies lead to more fast ion escape. In contrast, variations in the ICRF antenna phase exert only a marginal effect on fast-ion loss.

We developed a Monte Carlo simulation method to calculate incoherent Thomson scattering spectra in high temperature plasmas. The basic idea is to treat the entire scattering process as the superposition of individual photon-electron interactions. We introduce macro-particles, referred from particle-in-cell simulations, to reduce the computational cost, and obtain scattered spectra within a reasonable computational time. Since the velocity of the interacting electron is randomly sampled from an electron distribution function, the method can be applied to arbitrary electron distribution functions provided an appropriate sampling scheme is available. We present simulation results for relativistic Maxwellian and kappa distribution functions, and compare them with both analytical and numerical spectra for validation. The simulated spectra show good agreement with both analytical and numerical results, demonstrating that the Monte Carlo simulation method can reliably reproduce incoherent Thomson scattering spectra.

Tritium retention in plasma-facing components is a critical issue for fuel-cycle management in fusion reactors, and accurate evaluation of triton impact behavior is essential. To improve the fidelity of triton-wall interaction analysis in the Large Helical Device, we developed a high-accuracy computational and visualization framework that combines STL-based 3D models with VR-enabled representation of triton impact points and impact velocity vectors. D-D fusion born triton production was modeled using FIT3D-DD, and particle orbits were computed with LORBIT. Collision detection with plasma-facing structures was performed with high-resolution triangular mesh models exported from CAD designs. The STL-based wall model eliminated non-physical impact artifacts that appeared in the conventional cross-section-rotation geometry and provided physically consistent distributions of impact points. The visualization of impact velocity vectors within the VR environment enabled detailed qualitative assessment of incident-angle distributions, revealing geometric features−such as directional asymmetry between clockwise and counterclockwise toroidal magnetic field configurations− that cannot be captured by point-based visualization alone. This integrated approach demonstrates the effectiveness of combining precise geometric modeling with immersive VR visualization for interpreting energetic-particle behavior in fusion devices. The framework offers a valuable tool for correlating impact characteristics with material analyses and supports future optimization of plasma-facing component design.