Investigation of Stress/Strains and Related Properties in Superconducting Wires and Conductors by Means of Neutron Diffraction at J-PARC

Abstract

Synopsis:Recently the investigations on the local stress/strains and related properties in the engineered superconducting composites have been extensively carried out by using the pulsed neutron facilities, J-PARC TAKUMI. Firstly the key concepts are described in order to understand their mechanical-electromagnetic properties after the performance of TAKUMI is briefly introduced. Unique and important results have been obtained by the present diffraction studies. Highlights of the present review are the three dimensional description of strains in Nb 3 Sn filaments, the determination of force free strains at RT and 77 K for BSCCO and YBCO tapes, and of T o for the BSCCO tape and Nb 3 Sn wires, which is the initiation temperature of thermally induced residual strains. Typically the local axial strain exerted on Nb 3 Sn filaments has been firstly measured along the TF coil used for ITER project in the world.

Thermal Strain in Superconducting Nb3Sn Strand at Cryogenic Temperature

“…The thermal strains in the axial directions are largely compressive, while those in the transversal direction are near to zero. These tendencies are in good agreement with our previous results from thermal strains measurements in Nb 3 Sn strands at room temperature [5][6][7][8]. The strains in the axial direction decrease with decreasing temperature while those in the transversal direction slightly increase, resulting in increasing directional anisotropy.…”

“…It is well known that neutron diffraction can be used to measure internal strains, dislocation structures and texture in engineering materials [3,4]. We have measured residual strains using neutron diffraction in Nb 3 Sn filaments in different types of CICCs [5,6] or individually without embedded in CICC [5,7]. From the residual strain measurement in a CICC for the central solenoid (CS) magnet after a performance test of cyclic current at cryogenic temperature and high magnetic field, in full-size shape as used in the performance test (3.6 m long), we found a large relaxation of residual thermal strain in a cross sectional side where the Lorentz force coming in at high magnetic field zone [6,8].…”

Stress–strain behavior under static loading in Gd123 high-temperature superconductors at 77K

“…Since RE-Ba-Cu-O (RE: Y or rare-earth elements) HTS materials have intrinsic brittleness, evaluations of the mechanical properties are crucial. The homogeneities of various properties such as high fracture strength, high fracture toughness, high critical current density and low alternating current loss in long HTS conductors are indispensable for the practical application of superconducting devices [10][11][12].…”

“…Evaluations of the mechanical properties of RE123 materials are informative for further improvements of the mechanical properties of HTS conductors. With regard to the mechanical properties of RE123 materials, investigations about the residual strain in the RE123 materials of HTS conductors have been reported [11,12].…”

Non-destructive magneto-strain analysis of YB2Cu3Oy superconducting magnets using neutron diffraction in the time-of-flight mode

“…11 Several researchers have investigated residual strains in a variety of high-T c materials, including bulk form, first generation silver sheathed Bi-2223 or second generation Y-123 wire. [12][13][14] The cryogenic loading frame was also developed for the neutron diffraction strain measurements, 15 capable of 10 kN load and reaching temperature as low as 4.8 K. The investigators point out that the developed cryogenic load frame can be applied to the study of stress-strain effects in high-T c materials over a wide range of cryogenic temperatures. Until now there have been published no reports on neutron diffraction experiments on melt-processed superconductor bulks at lower temperatures with a trapped magnetic field.…”