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Full-Text Articles in Engineering
Superconducting Screening On Different Length Scales In High-Quality Bulk Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Alexey Pan, Xiaolin Wang
Superconducting Screening On Different Length Scales In High-Quality Bulk Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Alexey Pan, Xiaolin Wang
Xiaolin Wang
High-quality bulk MgB2 exhibits a structure of voids and agglomeration of crystals on different length scales. Because of this, the superconducting currents percolate between the voids in the ensuing structure. Magnetic measurements reveal that the superconducting currents circulate on at least three different length scales, of ∼1 μm, ∼10 μm, and whole of the sample (∼millimeter). Each of these screenings contributes to the measured irreversible magnetic moment (Δm). The analysis of the field dependence of Δm for samples of subsequently decreasing size showed that the critical current obtained using the simple critical state model is erroneous. This leads to the …
Effect Of Sample Size On Magnetic Jc For Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Xiaolin Wang, S. X. Dou
Effect Of Sample Size On Magnetic Jc For Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Xiaolin Wang, S. X. Dou
Xiaolin Wang
A strong effect of sample size on magnetic Jc(H) was observed for bulk MgB2 when Jc is obtained directly from the critical state model. Thus obtained zero-field Jc (Jc0) decreases strongly with the sample size, attaining a constant value for the samples larger than a few millimetres. On the other hand, the irreversibility field (Hirr) defined at Jc = 100 A/cm2 increases with the sample size. The decrease of Jc0 is described in terms of voids in the bulk MgB2 samples and superconducting screening around the cells of superconducting material between these voids (35 micro-m), because of concentration of the …
Superconducting Screening On Different Length Scales In High-Quality Bulk Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Alexey Pan, Xiaolin Wang
Superconducting Screening On Different Length Scales In High-Quality Bulk Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Alexey Pan, Xiaolin Wang
Saied Soltanian
High-quality bulk MgB2 exhibits a structure of voids and agglomeration of crystals on different length scales. Because of this, the superconducting currents percolate between the voids in the ensuing structure. Magnetic measurements reveal that the superconducting currents circulate on at least three different length scales, of ∼1 μm, ∼10 μm, and whole of the sample (∼millimeter). Each of these screenings contributes to the measured irreversible magnetic moment (Δm). The analysis of the field dependence of Δm for samples of subsequently decreasing size showed that the critical current obtained using the simple critical state model is erroneous. This leads to the …
Superconducting Screening On Different Length Scales In High-Quality Bulk Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Alexey Pan, Xiaolin Wang
Superconducting Screening On Different Length Scales In High-Quality Bulk Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Alexey Pan, Xiaolin Wang
Josip Horvat
High-quality bulk MgB2 exhibits a structure of voids and agglomeration of crystals on different length scales. Because of this, the superconducting currents percolate between the voids in the ensuing structure. Magnetic measurements reveal that the superconducting currents circulate on at least three different length scales, of ∼1 μm, ∼10 μm, and whole of the sample (∼millimeter). Each of these screenings contributes to the measured irreversible magnetic moment (Δm). The analysis of the field dependence of Δm for samples of subsequently decreasing size showed that the critical current obtained using the simple critical state model is erroneous. This leads to the …
The Relevance Of The Self-Field For The 'Peak Effect' In The Transport Jc(H) Of Iron-Sheathed Mgb2 Wires, J. Horvat, Saeid Soltanian, W. K. Yeoh
The Relevance Of The Self-Field For The 'Peak Effect' In The Transport Jc(H) Of Iron-Sheathed Mgb2 Wires, J. Horvat, Saeid Soltanian, W. K. Yeoh
Josip Horvat
Ferromagnetic sheath around a superconducting wire results in an unusual transport Jc(H). For the field perpendicular to the current, there is a plateau in Jc(H) at high temperatures and intermediate fields. This plateau develops into a peak at lower temperatures, resembling a “peak effect”. A model based on cancellation of the self-field of the current and external field within the iron sheath was proposed for the explanation of the plateau in Jc(H). We test this model in three key experiments. Firstly, we show that the form of Jc(H) for round MgB2/Fe wires is strongly temperature dependent. This is in contradiction …
Effect Of Sample Size On Magnetic Jc For Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Xiaolin Wang, S. X. Dou
Effect Of Sample Size On Magnetic Jc For Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Xiaolin Wang, S. X. Dou
Josip Horvat
A strong effect of sample size on magnetic Jc(H) was observed for bulk MgB2 when Jc is obtained directly from the critical state model. Thus obtained zero-field Jc (Jc0) decreases strongly with the sample size, attaining a constant value for the samples larger than a few millimetres. On the other hand, the irreversibility field (Hirr) defined at Jc = 100 A/cm2 increases with the sample size. The decrease of Jc0 is described in terms of voids in the bulk MgB2 samples and superconducting screening around the cells of superconducting material between these voids (35 micro-m), because of concentration of the …
Transport And Magnetic Critical Current In Superconducting Mgb2 Wires, J. Horvat, W. K. Yeoh, J. H. Kim, S. X. Dou
Transport And Magnetic Critical Current In Superconducting Mgb2 Wires, J. Horvat, W. K. Yeoh, J. H. Kim, S. X. Dou
Faculty of Engineering - Papers (Archive)
Direct comparison of the magnetic and transport critical current density (Jc) for the same pieces of copper-sheathed MgB2 wires shows a large discrepancy in magnitude and field dependence of the two. The value of magnetic Jc can differ from the value of transport Jc by a factor of 10 or more. This discrepancy does not occur merely because of the difference in the voltage at which the magnetic and transport Jc are measured, but mainly because of the specific microstructure of MgB2. Such microstructure results in superconducting screening on at least two different length-scales, despite the absence of weak links …