Strain Dependence of Critical Current in Internal Tin Process&amp;lt;tex&amp;gt;$rm Nb_3rm Sn$&amp;lt;/tex&amp;gt;Strands

We have developed a probe for the critical current measurements of low temperature superconducting strands at various field, temperature and strain. A 30 cm-long strand sample is soldered on a Walters spiral made of beryllium copper alloy and compressive or tensile axial strain can be applied up to 0.7%. Temperature control ability was tested using a MgB 2 wire up to 30 K. Three cernox sensors are attached on a spiral adjacent to the strand and the temperature of the spiral is controlled within 50 mK of target temperature during the critical current measurement up to 80 A. Extensive critical current measurements have been carried out for an internal-tin processed Nb 3 Sn strand. It was found that the measured field, temperature and strain dependence of the critical current for the internal-tin Nb 3 Sn strand is in agreement with the recent scaling law based on strong coupling theory of superconductivity.Index Terms-Eliashberg theory, scaling law for flux pinning, strain dependence of the critical current, Walters spiral probe.

Section: Development Of a Variable-temperature Walters Spiral Probesupporting

confidence: 56%

Section: Development Of a Variable-temperature Walters Spiral Probementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A Variable Temperature Walters Spiral Probe for the Critical Current Measurement of Superconducting Strands

Lee

Choi

et al. 2008

“…For comparison, the strain dependence of the critical current was also measured with a Walter spiral (WASP) probe [15] as shown in Fig. 4 as open symbols.…”

Section: Resultsmentioning

confidence: 99%

Reversible Transverse Stress Effects on the Critical Current of an Internal Tin ${\rm Nb}_{3}{\rm Sn}$Strand Under Axial Strain

Park

Lee

et al. 2010

We have developed an apparatus to investigate the effect of transverse stress under axial strain on the critical current of superconducting strands. An internal tin Nb 3 Sn wire is soldered on a C-shape ring (called Pacman) made of 2% beryllium doped copper alloy and axial strain from 0.7 to 0.7% can be applied. The actual strain on a sample was estimated from a comparison with the critical current measurement results using a Walter spiral probe. Reversible transverse stress effects on the critical current were studied in this work and the transverse pressure was applied up to 40 MPa under 0.5% axial strain. The critical current was initially increased about 3% as transverse load was applied and then decreased almost linearly under compressive axial strain. Similar behavior is observed under tensile axial strain but the critical current decreases rather sharply at higher load. A unified description based on 3 dimensional deviatoric strain was difficult for the sample studied in this work.Index Terms-Deviatoric strain, internal tin Nb 3 Sn, scaling law for flux pinning, strain dependence of the critical current, transverse stress effects.

“…A Mitsubishi (MELCO: Mitsubishi Electric Corporation) strand has been used for the construction of the KSTAR (Korea Superconducting Tokamak Advanced Research) superconducting magnet system. The strain dependences of the critical currents for the MELCO strand and a KAT (Kiswire Advanced Technology) strand at 4.2 K had been reported elsewhere [8]. The length of the sample used for the measurement is 10 mm for the MELCO strand and 5 mm for the KAT strand (KAT B strand in [8] Fig.…”

Section: Paramagnetic Backgroundmentioning

confidence: 98%

A Study on the Temperature Dependence of the Ginzburg-Landau Parameter, Thermodynamic and Upper Critical Field of ${\rm Nb}_{3}{\rm Sn}$ Strands

Bae

et al. 2007

We report detailed magnetization measurement results for two internal-tin Nb 3 Sn strands. The paramagnetic background of a Mitsubishi strand is about 4 times larger than that of a KAT strand below the transition temperature, which can be understood as combined effects of Pauli and Langevin paramagnetism. From magnetic relaxation measurement for the KAT strand, a possibility of surface barrier effect is discussed. After subtracting the paramagnetic background, reversible magnetization data are analysed using the Hao-Clem model and the Ginzburg-Landau parameters ( ), the thermodynamic and the upper critical fields ( 2 ) at various temperatures are obtained. The temperature dependences of , and 2 are compared with the recent theoretical calculation results for Nb 3 Sn and also with widely used empirical formulas.Index Terms-Eliashberg theory, paramagnetic background, superconducting parameters, the Hao-Clem model.