Papers by Author: Satoshi Awaji

Abstract: Researches to study internal stress/strain behaviors in industrial superconducting composites have been started at TAKUMI of J-PARC, as soon as the completion of TAKUMI construction. Preliminary results obtained from strains measurements during tensile deformation of Nb₃Sn strands and YBa₂Cu₃O₇ tapes, strains measurements during heating of Nb₃Sn strands and residual strains measurements in a Nb₃Sn Cable-In-Conduit Conductors are briefly described. The results can demonstrate possibilities of neutron engineering diffraction to solve problems in industrial superconducting composites by using J-PARC high flux neutron beam, even the volume fractions of superconducting phases in the composites are small and the superconducting phases locate inside the real components.

Abstract: A superconducting magnet with a magnetic energy of E = B2/2μo [J/m3] has to overcome a magnetic force of P = B2/2μo [Pa] in the same expression. This means that a high-field 20 T superconducting magnet produces an electromagnetic force of 160 MPa. In order to stand such a large force, Nb3Sn superconducting wires are usually reinforced by the hard-copper housing as an external reinforcement method or the stainless steel winding as a mechanical backup of an outermost Nb3Sn coil. If we focus on a compact superconducting magnet like a cryocooled superconducting magnet, a high-strength superconducting wire with a small diameter size of 1- 2 mm is required. The High-Field Laboratory for Superconducting Materials, IMR, Tohoku University has developed Nb3Sn wires internally reinforced with CuNb or CuNbTi composite. These high-strength Nb3Sn wires were successfully employed to construct the unique compact cryocooled 28 T hybrid magnet and the cryocooled 18 T high-temperature superconducting magnet. In addition, we found that the prebending effect for high-strength Nb3Sn wires outstandingly improves the Tc, Bc2 and Ic properties. As a next step, we intend to develop new Nb3Sn strand cables with the strong mechanical property of 500 MPa, applying the prebending effect for a future 22 T-φ400 mm room temperature bore superconducting magnet of a 50 T-class hybrid magnet.

Abstract: The current-carrying properties beyond a critical current determined by a voltage criterion for Ag-sheathed Bi2Sr2CaCu2O8 (Ag/Bi2212) superconductors are examined at 10 K and 20 K in magnetic fields. We prepared the in-field heat-treated Ag/Bi2212 wires, in order to obtain the magnetic field alignment microstructure for Ag/Bi2212. The electric field and current density (E-J) properties were evaluated for Ag/Bi2212 wires with and without the in-field heat-treatment. We found that the E-J properties for the in-field heat-treated Ag/Bi2212 wires differ from those for the out-of-field heat-treated ones, and are analogous to the E-J dependence for Bi-system high temperature superconductors with the sintered-like grain morphology.