Title :
High field flux pinning and the upper critical field of Nb-Ti superconductors
Author :
Naus, M.T. ; Heussner, R.W. ; Squitieri, A.A. ; Larbalestier, D.C.
Author_Institution :
Appl. Supercond. Center, Wisconsin Univ., Madison, WI, USA
fDate :
6/1/1997 12:00:00 AM
Abstract :
Nb-Ti wires of different composition and metallurgical state have been studied near the upper critical field (H/sub c2/) in an attempt to separate H/sub c2/ the irreversibility field (H*) and the resistively measured transition field (H/sub r/). For optimized multifilamentary Nb-47wt.%Ti wire, we find that H*=10.2 T, H/sub c2/=10.8 T and H/sub r/=11.8 T at 4.2 K. The transitions were studied by extended electric field vs. current density curves, magnetization and small current transport measurements. We found a strong correlation between magnetization, bulk flux pinning (F/sub p/) extrapolation and extended E-J curves for the value of H*, all giving H*=10.2 T. We have also shown that the maximum in H/sub r/ occurs for Nb-44wt.% Ti.
Keywords :
critical current density (superconductivity); flux pinning; magnetisation; multifilamentary superconductors; niobium alloys; superconducting critical field; titanium alloys; type II superconductors; 4.2 K; Nb-Ti; Nb-Ti superconductors; bulk flux pinning; current density; high field flux pinning; irreversibility field; magnetization; metallurgical state; optimized multifilamentary Nb-Ti wire; resistively measured transition field; small current transport; upper critical field; Critical current density; Current measurement; Extrapolation; Flux pinning; High temperature superconductors; Magnetic field measurement; Magnetization; Strain measurement; Superconductivity; Wires;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
