Characterisation of the Transport Critical Current Density for Conductor Applications

Raine, Mark J.; Keys, Simon A.; Hampshire, D.P.

doi:10.1201/9781003139638-13

Cited by 2 publications

(2 citation statements)

References 136 publications

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“…Standard four-terminal resistance measurements with a sample current of 100 mA were made over a temperature range from 70 − 95 K and in magnetic fields up to 8 T [23]. The current terminals and voltage taps were soldered directly to the sample itself using SnPb solder.…”

Section: B Sample Preparation and Measurementsmentioning

confidence: 99%

Resistivity Measurements of the Strain, Temperature and Angular Dependence of the Upper Critical Field of REBCO Tapes up to 8 T

Gillard,

Raine,

Hampshire

2023

IEEE Trans. Appl. Supercond.

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The design and operation of a miniature strainboard for measuring the resistivity of high temperature superconducting tapes as a function of uniaxial strain (ϵ) are described. It was used inside a Physical Property Measurement System (PPMS) that provides access to high fields, variable temperature, and a rotator that can vary the angle of the sample with respect to the field. Resistivity measurements made using the strain-board over the strain range 0% to −1.1% in-field are presented for a REBCO (REBa2Cu3O7, RE: Rare-earth element) tape from SuperPower with artificial pinning centres (APC). Values of the upper critical field (Bc2) were extracted from the resistivity data. We found that although the temperature and angular dependence of Bc2 were similar to that found in previous studies using ac susceptibility measurements (i.e. the temperature index, n = 1.2 , the anisotropy constant, γ = 1.4 and the interlayer spacing s = 12 Å), the upper critical field we found was almost strain independent and therefore quite different. We explain these results by considering the bimodal behaviour of REBCO under strain that is found in single crystal data, and the large parallel shunt the strain-board provided in the measurements. In our resistivity measurements, Bc2 is determined by a small percolative supercurrent that preferentially flows through material with the highest critical parameters. Conversely, resistivity measurements at high currents, or ac susceptibility measurements, characterise the material with average or low critical parameters from the broad distribution of critical parameters produced in REBCO tapes under strain.

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Section: B Sample Preparation and Measurementsmentioning

confidence: 99%

Resistivity Measurements of the Strain, Temperature and Angular Dependence of the Upper Critical Field of REBCO Tapes up to 8 T

Gillard,

Raine,

Hampshire

2023

IEEE Trans. Appl. Supercond.

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“…The 6000 A shunt was calibrated and corrected by 0.64 % from it's nominal value. In this work, four-terminal I c measurements were made with a continuously ramped current, as well as bath temperature readings [6], [7]. The measurements were made using a nano-amplifier (× 50k gain) to obtain low noise data (± 4 µVm −1 ) and without the nano-amplifier to obtain data at higher electric fields (∼ 800 µVm −1 , see Figure 3 for the core).…”

Section: Experimental Setup and Analysismentioning

confidence: 99%

HTS Cable International Round Robin: 4.4 kA Critical Current Measurements

Hutson

Raine

Kiuchi

et al. 2023

IEEE Trans. Appl. Supercond.

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The critical current of the core and shield of a 2.1 m long, 40 mm diameter Bi-2223 HTS coaxial cable was measured as part of an International Round Robin organised by Japan involving several international laboratories. In Durham, we found using a 100 µVm −1 criterion and an 8 minute trace time that Ic of the core and shield were 4386 A and 4143 A and the nvalues were 19.6 and 14.4 respectively. 8 minute trace times were found to be a practical approximation of steady state conditions, with critical current values 0.5 % and 1.2 % larger than values obtained using 2 minute trace times, and n-values not significantly different to 2 minute trace values. Two minute trace time data were compared with equivalent data from other participating labs and excellent agreement was found: Ic was 0.6 % and 1.5 % larger for the core and shield respectively. The E-field range has a significant effect on the n-value measurements, which varied between groups. Good agreement between the participants for the shield was found for electric fields below 100 µVm −1 , although larger n-values were found at higher electric fields at Durham and some other laboratories. The polarity of the current and the proximity of the return power cable were demonstrated to have negligible effect (< 0.1 %) on the Ic measurements. Removing conductive and ferromagnetic materials that were part of Durham's experimental set-up increased Ic by < 1 %. An intrinsic trace time dependency was found for Ic for trace times of less than 8 minutes that we attribute to the time required for fluxons to equilibrate with the underlying pinning landscape in a changing net magnetic field.

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Characterisation of the Transport Critical Current Density for Conductor Applications

Cited by 2 publications

References 136 publications

Resistivity Measurements of the Strain, Temperature and Angular Dependence of the Upper Critical Field of REBCO Tapes up to 8 T

Resistivity Measurements of the Strain, Temperature and Angular Dependence of the Upper Critical Field of REBCO Tapes up to 8 T

HTS Cable International Round Robin: 4.4 kA Critical Current Measurements

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