The unified strain and temperature scaling law for the pinning force density of bronzeroute Nb _{3}Sn wires in high magnetic fields
Abstract
Detailed measurements of the critical current density ( J_{c}) of a bronzeroute niobiumtin wire are presented for magnetic fields ( B) up to 15 T as a function of temperature ( T) from 6 K up to 16 K in the strain ( ∊) range between 0.7% and +0.7%. The data for this technological wire are described by a unified strain and temperature scaling law for the pinning force density of the form F _{p}(B,T,∊)=J _{c}×B=A(∊)[B _{c2}^{∗}(T,∊)] ^{n}b ^{p}(1b) ^{q}, where A( ∊) is a function of strain alone, B _{c2}^{∗} is the effective upper critical field at which F_{p} extrapolates to zero, b=B/B _{c2}^{∗} is the reduced magnetic field and n, p and q are constants. It is demonstrated that were A(∊)(B _{c2}^{∗}) ^{n} replaced by F(T)(B _{c2}^{∗}) ^{m} where F( T) is a function of temperature alone, the strain index m is a strong function of temperature and strain, and in high compression m= n. The effective upper critical field can be parameterized using the expression B _{c2}^{∗}(T,∊)=B _{c2}^{∗}(0,∊)(1(T/T _{c}^{∗}(∊)) ^{ν}) , where ν is a constant and T _{c}^{∗}(∊) is the effective critical temperature at which B _{c2}^{∗} at a given strain extrapolates to zero. The strain dependence of the ratio B _{c2}^{∗}(0,∊)/T _{c}^{∗}(∊) and the slope ( ∂B _{c2}^{∗}(T,∊)/ ∂T) _{T=T c∗(∊) } is reported. The data presented are useful for cryocooled high field magnets and for identifying the mechanisms that determine J_{c} in niobiumtin superconducting wires.
 Publication:

Cryogenics
 Pub Date:
 May 2002
 DOI:
 10.1016/S00112275(02)000383
 Bibcode:
 2002Cryo...42..299C