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Probes for investigating the effect of magnetic field, field orientation, temperature and strain on the critical current density of anisotropic high-temperature superconducting tapes in a split-pair 15 T horizontal magnet.
Rev Sci Instrum 2014; 85(6):065111RS

Abstract

We present the designs of probes for making critical current density (Jc) measurements on anisotropic high-temperature superconducting tapes as a function of field, field orientation, temperature and strain in our 40 mm bore, split-pair 15 T horizontal magnet. Emphasis is placed on the design of three components: the vapour-cooled current leads, the variable temperature enclosure, and the springboard-shaped bending beam sample holder. The vapour-cooled brass critical-current leads used superconducting tapes and in operation ran hot with a duty cycle (D) of ~0.2. This work provides formulae for optimising cryogenic consumption and calculating cryogenic boil-off, associated with current leads used to make J(c) measurements, made by uniformly ramping the current up to a maximum current (I(max)) and then reducing the current very quickly to zero. They include consideration of the effects of duty cycle, static helium boil-off from the magnet and Dewar (b'), and the maximum safe temperature for the critical-current leads (T(max)). Our optimized critical-current leads have a boil-off that is about 30% less than leads optimized for magnet operation at the same maximum current. Numerical calculations show that the optimum cross-sectional area (A) for each current lead can be parameterized by LI(max)/A = [1.46D(-0.18)L(0.4)(T(max) - 300)(0.25D(-0.09)) + 750(b'/I(max))D(10(-3)I(max)-2.87b') × 10⁶ A m⁻¹ where L is the current lead's length and the current lead is operated in liquid helium. An optimum A of 132 mm(2) is obtained when I(max) = 1000 A, T(max) = 400 K, D = 0.2, b' = 0.3 l h(-1) and L = 1.0 m. The optimized helium consumption was found to be 0.7 l h(-1). When the static boil-off is small, optimized leads have a boil-off that can be roughly parameterized by: b/I(max) ≈ (1.35 × 10(-3))D(0.41) l h(‑1) A(-1). A split-current-lead design is employed to minimize the rotation of the probes during the high current measurements in our high-field horizontal magnet. The variable-temperature system is based on the use of an inverted insulating cup that operates above 4.2 K in liquid helium and above 77.4 K in liquid nitrogen, with a stability of ±80 mK to ±150 mK. Uniaxial strains of -1.4% to 1.0% can be applied to the sample, with a total uncertainty of better than ±0.02%, using a modified bending beam apparatus which includes a copper beryllium springboard-shaped sample holder.

Authors+Show Affiliations

Superconductivity Group, Centre for Materials Physics, Department of Physics, University of Durham, Durham DH1 3LE, United Kingdom.Superconductivity Group, Centre for Materials Physics, Department of Physics, University of Durham, Durham DH1 3LE, United Kingdom.Superconductivity Group, Centre for Materials Physics, Department of Physics, University of Durham, Durham DH1 3LE, United Kingdom.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

24985856

Citation

Sunwong, P, et al. "Probes for Investigating the Effect of Magnetic Field, Field Orientation, Temperature and Strain On the Critical Current Density of Anisotropic High-temperature Superconducting Tapes in a Split-pair 15 T Horizontal Magnet." The Review of Scientific Instruments, vol. 85, no. 6, 2014, p. 065111.
Sunwong P, Higgins JS, Hampshire DP. Probes for investigating the effect of magnetic field, field orientation, temperature and strain on the critical current density of anisotropic high-temperature superconducting tapes in a split-pair 15 T horizontal magnet. Rev Sci Instrum. 2014;85(6):065111.
Sunwong, P., Higgins, J. S., & Hampshire, D. P. (2014). Probes for investigating the effect of magnetic field, field orientation, temperature and strain on the critical current density of anisotropic high-temperature superconducting tapes in a split-pair 15 T horizontal magnet. The Review of Scientific Instruments, 85(6), p. 065111. doi:10.1063/1.4881235.
Sunwong P, Higgins JS, Hampshire DP. Probes for Investigating the Effect of Magnetic Field, Field Orientation, Temperature and Strain On the Critical Current Density of Anisotropic High-temperature Superconducting Tapes in a Split-pair 15 T Horizontal Magnet. Rev Sci Instrum. 2014;85(6):065111. PubMed PMID: 24985856.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Probes for investigating the effect of magnetic field, field orientation, temperature and strain on the critical current density of anisotropic high-temperature superconducting tapes in a split-pair 15 T horizontal magnet. AU - Sunwong,P, AU - Higgins,J S, AU - Hampshire,D P, PY - 2014/7/3/entrez PY - 2014/7/6/pubmed PY - 2014/7/6/medline SP - 065111 EP - 065111 JF - The Review of scientific instruments JO - Rev Sci Instrum VL - 85 IS - 6 N2 - We present the designs of probes for making critical current density (Jc) measurements on anisotropic high-temperature superconducting tapes as a function of field, field orientation, temperature and strain in our 40 mm bore, split-pair 15 T horizontal magnet. Emphasis is placed on the design of three components: the vapour-cooled current leads, the variable temperature enclosure, and the springboard-shaped bending beam sample holder. The vapour-cooled brass critical-current leads used superconducting tapes and in operation ran hot with a duty cycle (D) of ~0.2. This work provides formulae for optimising cryogenic consumption and calculating cryogenic boil-off, associated with current leads used to make J(c) measurements, made by uniformly ramping the current up to a maximum current (I(max)) and then reducing the current very quickly to zero. They include consideration of the effects of duty cycle, static helium boil-off from the magnet and Dewar (b'), and the maximum safe temperature for the critical-current leads (T(max)). Our optimized critical-current leads have a boil-off that is about 30% less than leads optimized for magnet operation at the same maximum current. Numerical calculations show that the optimum cross-sectional area (A) for each current lead can be parameterized by LI(max)/A = [1.46D(-0.18)L(0.4)(T(max) - 300)(0.25D(-0.09)) + 750(b'/I(max))D(10(-3)I(max)-2.87b') × 10⁶ A m⁻¹ where L is the current lead's length and the current lead is operated in liquid helium. An optimum A of 132 mm(2) is obtained when I(max) = 1000 A, T(max) = 400 K, D = 0.2, b' = 0.3 l h(-1) and L = 1.0 m. The optimized helium consumption was found to be 0.7 l h(-1). When the static boil-off is small, optimized leads have a boil-off that can be roughly parameterized by: b/I(max) ≈ (1.35 × 10(-3))D(0.41) l h(‑1) A(-1). A split-current-lead design is employed to minimize the rotation of the probes during the high current measurements in our high-field horizontal magnet. The variable-temperature system is based on the use of an inverted insulating cup that operates above 4.2 K in liquid helium and above 77.4 K in liquid nitrogen, with a stability of ±80 mK to ±150 mK. Uniaxial strains of -1.4% to 1.0% can be applied to the sample, with a total uncertainty of better than ±0.02%, using a modified bending beam apparatus which includes a copper beryllium springboard-shaped sample holder. SN - 1089-7623 UR - https://www.unboundmedicine.com/medline/citation/24985856/Probes_for_investigating_the_effect_of_magnetic_field_field_orientation_temperature_and_strain_on_the_critical_current_density_of_anisotropic_high_temperature_superconducting_tapes_in_a_split_pair_15_T_horizontal_magnet_ L2 - https://dx.doi.org/10.1063/1.4881235 DB - PRIME DP - Unbound Medicine ER -