Search

Your search keyword '"Hashizume, Hidetoshi"' showing total 401 results
Start Over Author "Hashizume, Hidetoshi"
401 results on '"Hashizume, Hidetoshi"'

9. Quench Detection in Insulated, NI, and MI (RE)Ba2Cu3O7–x Coils With Superconducting Quench Detectors

Author

Hasegawa, Shin, Ito, Satoshi, Nishijima, Gen, Awaji, Satoshi, Takahashi, Kohki, and Hashizume, Hidetoshi

Abstract

In this article, we have proposed a quench detection method that uses a low-temperature superconducting quench detector (LTS QD) for rare-earth barium copper oxide (REBCO) coils at 4.2 K. Previous studies demonstrated the quench detection with an LTS QD in a layer-wound REBCO coil. In this study, the quench detection performance of LTS QDs for insulated, no-insulation (NI), and metal-as-insulation (MI) REBCO pancake coils was experimentally compared. An experiment that used a Nb–Ti/Cu–Ni QD installed in insulated, NI, and MI REBCO coils demonstrated a quench detection before a thermal runaway in the coil at 4.2 K and 0–9 T. The Nb–Ti/Cu–Ni QD showed slower quench detection in the coils without turn-to-turn insulation. It would be due to the small heat density around the hot spot and large heat exchange between the Nb–Ti/Cu–Ni QD and REBCO coils. In conclusion, this study indicated that the turn-to-turn resistance in the REBCO coil and thermal gap conductance between the coil and the LTS QD are key parameters for the design of LTS QDs. Moreover, the feasibility of the quench detection with appropriate LTS QDs for the insulated, NI, and MI REBCO pancake coils was demonstrated at 4.2 K.

Published
2024
Full Text
View/download PDF

36. Design of a simple side-incident TE11 mode microwave probe for nondestructive pipe inspection.

Author

Guo, Yijun, Yoshikawa, Ryo, Yusa, Noritaka, and Hashizume, Hidetoshi

Subjects
MICROWAVES, COAXIAL cables, ELECTROMAGNETIC fields, COPLANAR waveguides, WIRE
Abstract

This study proposed a simple side-incident TE11 mode microwave probe for the rapid and long-range inspection of cracks in metallic pipes. The probe feeds the microwaves to a metallic pipe, which works as a waveguide; the reflection signal provoked by a defect is measured for detection and localization. The probe enables the detection of both circumferentially and axially oriented cracks, unlike those reported in earlier studies. To achieve better performance, numerical simulations were conducted to evaluate the conversion efficiency and optimize the insertion length of the coaxial cable and the exposed length of the cable core wire. The simulation results suggest that the optimized probe configuration is feasible for pipes with various diameters by proportionally changing the current probe configuration. Although injected microwaves propagated in two directions, the ratio of microwaves to one direction could be controlled by adjusting the inclination angle and the exposed length of the cable core wire. Subsequently, three TE11 probes fabricated according to the simulation results were used to detect circumferential and axial slits in a brass pipe. The results showed that circumferential slits in the vertical positions (parallel to the nontilted coaxial cable) and axial slits in the horizontal positions (perpendicular to the nontilted coaxial cable) caused large reflections, consistent with the electromagnetic field distribution of the TE11 mode microwaves in a circular waveguide. Further experiments verified the feasibility of the designed probe for pipes with different diameters and for directional pipe inspection. [ABSTRACT FROM AUTHOR]

Published
2023
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results