Enhancement of the superconducting critical current from saturation in Nb-Ti wire. I

Journal Article · Sun May 15 00:00:00 EDT 1988 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.340402· OSTI ID:5187039

Matsushita, T; Kuepfer, H

The flux pinning characteristic of processed Nb-Ti monofilamentary wires was investigated at 4.2 K and higher temperatures by an ac measuring method. Saturation of the global pinning force, as in Nb/sub 3/Sn, was observed at high fields for specimens heat treated after initial heavy cold work. A transition from the saturation to a strongly pinned nonsaturation occurred after the specimen was finally cold worked. This transition directly demonstrates that the saturation is not caused by a shearing deformation of the fluxoid lattice assumed in Kramer's model (J. Appl. Phys. 44, 1360 (1973)), because this proposed mechanism primarily depends on intrinsic superconducting properties which are not changed by the final cold working. From the measurements of the elastic and plastic behavior of the fluxoid lattice by using the ac method, it was also found that it was not the shearing deformation of the fluxoid lattice but rather the depinning that occurred in the saturation: The saturation is expected to be caused by a catastrophic avalanching flow of the brittle fluxoid lattice. The transition can be explained by an increase of the elementary pinning force of normal Ti precipitates due to elongation by the cold work. The present result and existing results on various materials suggest that the nonsaturation is attained by increasing the elementary pinning force and/or the pin concentration.

• Research Organization: Kernforschungszentrum and Universitaet Karlsruhe, Institut f uer Technische Physik, 7500 Karlsruhe, Federal Republic of Germany
• OSTI ID: 5187039
• Journal Information: J. Appl. Phys.; (United States), Vol. 63:10
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
NIOBIUM BASE ALLOYS
CRITICAL CURRENT
MAGNETIC FLUX
SUPERCONDUCTING WIRES
FABRICATION
TITANIUM ALLOYS
DEFORMATION
ELASTICITY
EXPERIMENTAL DATA
PLASTICITY
SATURATION
ALLOYS
CURRENTS
DATA
ELECTRIC CURRENTS
INFORMATION
MECHANICAL PROPERTIES
NIOBIUM ALLOYS
NUMERICAL DATA
TENSILE PROPERTIES
WIRES
360104* - Metals & Alloys- Physical Properties
656100 - Condensed Matter Physics- Superconductivity
420201 - Engineering- Cryogenic Equipment & Devices