Specific Heat, A Method to Determine the $T_{c}$ Distribution in Industrial ${\rm Nb}_{3}{\rm Sn}$ Wires Prepared by Various Techniques

Senatore, Carmine; Uglietti, D.; Abächerli, V.; Junod, A.; Flükiger, R.

doi:10.1109/tasc.2007.897928

Cited by 21 publications

(26 citation statements)

References 9 publications

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“…The superconducting contributions to specific heat were then analysed by means of a particular deconvolution method in order to determine the distribution of [13]. The advantage of calorimetry compared to other techniques is that the distribution is obtained for the whole sample volume, ruling out percolation and/or shielding effects.…”

Section: Specific Heat Measurementsmentioning

confidence: 99%

Enhanced Connectivity and Percolation in Binary and Doped In Situ ${\rm MgB}_{2}$ Wires After Cold High Pressure Densification

Senatore

Hossain

Flükiger

2011

IEEE Trans. Appl. Supercond.

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The cold high pressure densification technique (CHPD) was recently developed in Geneva for improving the in-field critical current density of in situ binary and alloyedMgB 2 wires and tapes [1], [2]. of CHPD treated square wires alloyed with malic acid (C 4 H 6 O 5 ) was enhanced by a factor 2 at 10 T and 4.2 K. In order to understand the fundamental mechanism behind this strong improvement of , the properties of binary and alloyed MgB 2 wires have been investigated without and with CHPD, using resistivity and specific heat measurements in the temperature range from 5 to 35 K in magnetic fields up to 15 T. In particular, a deconvolution of the specific heat data was used to determine the distribution of in the samples. We have found that the effect of the densification process on the electrical and transport properties is related to the improved grain connectivity and percolation. By combining the results arising from the analysis of the distribution and those from resistivity measurements, it is concluded that the minimum superconducting volume fraction needed for the percolation of a superconducting path is strongly reduced in samples treated by CHPD.

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Section: Specific Heat Measurementsmentioning

confidence: 99%

Enhanced Connectivity and Percolation in Binary and Doped In Situ ${\rm MgB}_{2}$ Wires After Cold High Pressure Densification

Senatore

Hossain

Flükiger

2011

IEEE Trans. Appl. Supercond.

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“…15 Data from such a measurement performed on the very same sample we examined were available from previous work. As shown in Figure 4 by the red curve, whose individual data points are indicated by squares, the calorimetry histogram is much broader than the one we obtained.…”

Section: Compute the Magnetic Moment Resultingmentioning

confidence: 99%

Assessing composition gradients in multifilamentary superconductors by means of magnetometry methods

Baumgartner

Hecher

Bernardi

et al. 2016

Supercond. Sci. Technol.

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We present two magnetometry-based methods suitable for assessing gradients in the critical temperature and hence the composition of multifilamentary superconductors: AC magnetometry and Scanning Hall Probe Microscopy. The novelty of the former technique lies in the iterative evaluation procedure we developed, whereas the strength of the latter is the direct visualization of the temperature dependent penetration of a magnetic field into the superconductor. Using the example of a PIT Nb3Sn wire, we demonstrate the application of these techniques, and compare the respective results to each other and to EDX measurements of the Sn distribution within the sub-elements of the wire.

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“…The superconducting transition of the filaments was isolated from the background of phonons and normal state electrons, as determined from the curves measured at 14 T, following the procedure described in [2]. The data were then analysed by means of a particular deconvolution method in order to determine the distribution of in the A15 layer [2]. The superconducting transition was also characterized inductively using a SQUID (Superconducting Quantum Interference Device).…”

Section: Sample Description and Experimentalmentioning

confidence: 99%

Phase Formation, Composition and ${\rm T}_{\rm c}$ Distribution of Binary and Ta-Alloyed ${\rm Nb}_{3}{\rm Sn}$ Wires Produced by Various Techniques

Senatore

Mondonico

Buta

et al. 2012

IEEE Trans. Appl. Supercond.

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Low temperature calorimetry was used to determine the distribution of the superconducting transition temperature in binary and Ta-doped wires fabricated by the Bronze route and by the Powder-In-Tube (PIT) method. From this analysis we were able to discern the effects of Sn and Ta compositions on the distribution of the superconducting parameters and in the different samples. The influence of the heat treatment conditions on the superconducting properties was investigated for the PIT wires. In particular we determined the field dependence of the distribution for a commonly used reaction schedule (675 /84 h) and for an optimized heat treatment (625 /320 h). For the first time, we show that the wire reacted at 625 /320 h exhibits two separated contributions in the distribution directly related to the grain morphology of the A15 layer: a narrow peak determined by the large grains, with a lower , and a broad peak due to the fine grains, with a higher . The kinetics of the Sn diffusion in Nb and the growth rate of the A15 layer were experimentally studied. The influence of Ta doping on the A15 phase formation was analysed by electron microscopy, the growth rate and the grain morphology in binary and Ta-alloyed Bronze route wires with the same filament layout being compared at different stages of the heat treatment. At the end of reaction, the well known microstructure comprising equiaxed and columnar regions was observed in the filaments of both the binary and the Ta-alloyed wires. Based on these observations and from the growth rate analysis we conclude that Ta does not affect the Sn diffusion rate.

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Specific Heat, A Method to Determine the $T_{c}$ Distribution in Industrial ${\rm Nb}_{3}{\rm Sn}$ Wires Prepared by Various Techniques

Cited by 21 publications

References 9 publications

Enhanced Connectivity and Percolation in Binary and Doped In Situ ${\rm MgB}_{2}$ Wires After Cold High Pressure Densification

Enhanced Connectivity and Percolation in Binary and Doped In Situ ${\rm MgB}_{2}$ Wires After Cold High Pressure Densification

Assessing composition gradients in multifilamentary superconductors by means of magnetometry methods

Phase Formation, Composition and ${\rm T}_{\rm c}$ Distribution of Binary and Ta-Alloyed ${\rm Nb}_{3}{\rm Sn}$ Wires Produced by Various Techniques

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