Speaker
Prof.
Kohei Higashikawa
(Kyushu University)
Description
We have succeeded in characterizing critical current properties of recent high-performance MgB2 wires at very high critical current conditions. Generally, critical currents of a wire are measured by four-probe transport measurements. However, for high critical current conditions, e.g., at relatively low magnetic fields, it is difficult to perform the measurement due to heat generation and/or the limitation of experimental system. This is one reason why the performances of the wires are often reported for high external magnetic field conditions, e.g., at higher than 5 T. On the other hand, one of the most promising applications for MgB2 wires is MRI where the wire experiences much lower external magnetic field. This means that some characterization method for such conditions is indispensable for MgB2 wire development and for MRI magnet design. As a complementary method, magnetization measurement is often used to estimate critical current densities. However, we cannot apply this method to recent high-performance MgB2 wires because a simple magnetization pattern cannot be assumed due to their magnetic sheath materials and spatial inhomogeneity.
In this study, we established a characterization method of critical current properties for the MgB2 wires based on scanning Hall-probe microscopy. Magnetic field distribution on a magnetized wire was measured, and then the value of critical current which could express it quantitatively was estimated. As a result, we successfully evaluated critical current values as hundreds to a thousand amperes without a transport current. Furthermore, it was confirmed that the results agreed very well with the extrapolation from the properties obtained by the four-probe transport method. We will show critical current properties of internal-Mg-diffusion-processed wires where the performances have been dramatically improved recently as the second generation wires.
This work was partly supported by JST as ALCA.
Author
Prof.
Kohei Higashikawa
(Kyushu University)
Co-authors
Dr
Akiyoshi Matsumoto
(National Institute for Materials Science)
Dr
Guangze Li
(Ohio State University)
Prof.
Hiroaki Kumakura
(National Institute for Materials Science)
Mr
Masato Kamihigoshi
(Kyushu University)
Prof.
Masayoshi Inoue
(Kyushu University)
Dr
Matthew Rindfleisch
(Hyper Tech Research, Incorporated)
Prof.
Michael Sumption
(Ohio State University)
Dr
Michael Tomsic
(Hyper Tech Research, Incorporated)
Dr
Shujun Ye
(National Institute for Materials Science)
Prof.
Takanobu Kiss
(Kyushu University)
Mr
Yuan Yang
(Ohio State University)
