2008　論文

2008年

1:Influence of deviatoric strain
　　　for superconducting parameters of Nb₃Sn wires
Oguro, H; Awaji, S; Nishijima, G; et al.
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 18　(2008)　1047-1050

Abstract
The tensile strain dependence of the upper critical field B_c2 for Nb₃Sn wires was measured using a new apparatus for applying tension at low temperature. The critical current I_c calculated from the strain-dependent B_c2 measurements is the almost consistent with the measured I_c. In the measurements by a new apparatus, the axial and the lateral applied strains were examined by the strain gauges attached onto the wire. The deviatoric strain ε_dev and the hydrostatic strain ε_hyd were estimated by the axial and the lateral strain. We found the deviatoric strain dependence of B_c2 is different between the tensile and compressive strain states. This means that the hydrostatic strain also should be taken into account in order to understand the strain effects on the superconducting properties of Nb₃Sn.

2:Effect of c-axis-correlated disorders
　　on the vortex diagram of the pinning state
Namba, M; Awaji, S; Watanabe, K; et al.
APPLIED PHYSICS EXPRESS 1　(2008) 031703　1-3

Abstract
The introduction of the c-axis-correlated disorder is a promising technique for the improvement of the critical current density J_c for B // c of REBa2Cu3Oy (RE123) films and tapes. In order to understand the vortex pinning mechanism with the different variety of the c-axis-correlated disorder, the angular dependence of J_c was measured in detail for an Y123 film with BaZrO3 nano-rods, a Sm123 film with fine nano-particles and edge dislocations and an Y123 film with columnar defects introduced by the heavy-ion irradiation parallel to the c-axis. We found that the vortex pinning state for the variety of the c-axis-correlated pinning is similar in low fields below the matching field, but it shows different behaviors in high fields above the matching field. It is considered that the interstitial vortices interacted with the c-axis-correlated disorders through the vortex interaction may play an important role for the appearance of the c-axis-correlated pinning behavior in a high-field region above the matching field.

3:c-Axis-correlated pinning properties in heavy-ion-irradiated Y123 films
Namba, M.; Awaji, S.; Watanabe, K.; et al.
Physica C 468,15-20 (2008) 1652-1655

Abstract
The introduction of the c-axis-correlated disorder is a promising technique for the improvement of the critical current density J_c for B ∥ c of the REBa₂Cu₃O_y films and tapes. In order to understand the vortex pinning state diagram of typical c-axis-correlated disorder, the angular dependence of J_c was measured in detail for Y123 films with columnar defects induced by heavy-ion irradiation. We found that the peak in the angular dependence of J_c at the parallel external field to the c-axis (B ∥ c) becomes sharp and large with increasing a magnetic field across the matching magnetic field at various temperatures. Hence, the c-axis-correlated pinning works well even in much higher magnetic fields than the matching magnetic field. Those behaviors suggest that the interstitial vortices, which locate in between vortices pinned by the c-axis-correlated disorders, are also trapped through the elastic interaction of the vortices.