Bi2223 チョウデンドウ フクゴウ テープザイ ノ デンジ リキガクテキ トクセイ

京都大学0048新制・課程博士博士(工学)甲第10378号工博第2296号新制||工||1287(附属図書館)UT51-2003-L19京都大学大学院工学研究科材料工学専攻(主査)教授 長村 光造, 教授 牧 正志, 教授 落合 庄治郎学位規則第4条第1項該当Doctor of EngineeringKyoto UniversityDA

Influences of Electroplated Copper on Tensile Strain and Stress Tolerance of Critical Current in DyBCO-Coated Conductor

This paper was carried out to reveal the influence of plated copper onto the substrate tape constituting of DyBa2Cu3O7-δ, MgO, Ag, and Hastelloy C-276 on the stress-strain behavior, and tensile strain and stress tolerance of critical current at 77 K. From the analysis of the stress-strain relation of the copper-plated tape at 77 K, it was shown that the copper plated at room temperature is yielded in tension at 77 K due to the higher coefficient of the thermal expansion of copper than that of the substrate tape. The plated copper gave compressive strain to the substrate tape and, hence, the superconducting layer at 77 K, due to which the strain tolerance of critical current was improved. The observed improvement of the strain tolerance with increasing volume fraction of plated copper was quantitatively described from the viewpoint of the stress balance at 77 K between the substrate tape and yielded copper. The tolerant strain increased, but the tolerant stress decreased with increasing copper volume fraction. Such a tradeoff correlation between the tolerant strain and stress was well described by modeling analysis

Stress Analysis of a High Temperature Superconductor Coil Wound With Bi-2223/Ag Tapes for High Field HTS/LTS NMR Magnet Application

The electromagnetic stress distribution inside a HTS insert is one of the key issues for construction of a high field high/low temperature superconductor (HTS/LTS) magnet. The rmiddotJmiddotB formulae is widely used for the stress calculation of the coil, due to its simplicity. However, the assumption of this calculation makes it impossible to consider the effects of the bobbin, an epoxy impregnated structure, on stress of the coil. In this work, stress analysis methods are reported. The governing equation defined from the force equilibrium state was adopted and used to analyze what the stress of the HTS coil wound with Bi2223/Ag conductor. The validness of the stress analysis method was confirmed by comparison with experimental results, especially in the coil with epoxy impregnation. The numerical and experimental procedures are described and both results are discussed.Budget for Nuclear Research of the Ministry of Education, Culture, Sports, Science and TechnologyJapan Science and Technology (JST)System Development Program for Advanced Measurement and Analysis (SENTAN

The characteristics of Bi-2223/Ag conductor for high field application

For the development of high magnetic field application using high temperature superconductor (HTS), Bi-2223/Ag tape is one of the promising materials because of its high current capacity and upper critical field. However, Bi-2223/Ag tape shows very strong anisotropy and significant deterioration of critical current in the magnetic field. To explore the possibility of HTS in high field applications, we evaluated the critical current and index value of Bi-2223/Ag conductor in high magnetic field. The Bi-2223/Ag tape was characterized as a function of increasing and decreasing field. The temperature dependence was also examined lower than 4.2 K. All measurements were carried out with hybrid magnet system up to 30 T and the experimental results are reported

Field Quality and Mechanical Analysis of the Beam Separation Dipole for HL-LHC Upgrade

High luminosity upgrade of the Large Hadron Collider (HL-LHC) project has been launched to attain a ten times higher integrated luminosity than the current LHC that has been in operation for over ten years. For this goal, the quadruple and dipole magnets around two interaction points, the ATLAS and the CMS, will be upgraded. High Energy Accelerator Research Organization (KEK) is in charge of developing the new superconducting beam separation dipole magnet (D1). The main dipole field of 5.6 T in a large aperture of 150 mm is generated using a cos-theta coil wound with Nb-Ti cables at nominal operating current of 12.0 kA at 1.9 K corresponding to 75% of the load line ratio. The main challenges for the D1 are larger aperture, a high level of iron saturation, radiation resistance, and tight constraints on field quality. This article summarizes the results of a detailed analysis on field error. Electromagnetic simulation with ROXIE was carried out for the 2-D model of the new D1. As possible design changes, a diameter and position of heat exchanger holes in the iron yoke, and shape of the cryostat were considered. To reveal the influence on systematic error, packing factor of iron yoke, relative permeability of the stainless steel collar, and coil deformation during yoking were reflected to the baseline design. In addition, random geometric error was also estimated. Based on these results, contribution of each factor to field quality is studied