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Selected Works

2008

Size-effect

Articles 1 - 5 of 5

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 May 2008

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 May 2008

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 May 2008

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 May 2008

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 …


Effect Of Sample Size On Magnetic Jc For Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Xiaolin Wang, S. X. Dou May 2008

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 …