L'invention concerne un dispositif et un procede pour la formation continue de fil supracondu... more L'invention concerne un dispositif et un procede pour la formation continue de fil supraconducteur et les produits fabriques a partir du fil. Le procede peut comprendre la fourniture d'au moins une bande de revetement metallique continue et au moins une forme metallique, formant en continu une bande de revetement metallique continue pour former une configuration partiellement ouverte, remplissant en continu la configuration partiellement ouverte de precurseur a base de diborure de magnesium comprenant du bore, et une forme metallique, et fermant la configuration partiellement ouverte, enfermant ainsi le precurseur a base de diborure de magnesium comprenant du bore, et une forme metallique, pour former une configuration fermee. Une reduction ulterieure du diametre et un allongement de la longueur de la configuration fermee, suivies d'un traitement thermique, catalysent la transformation du precurseur a base de diborure de magnesium comprenant du bore, et la forme metalliq...
To reduce the usage of liquid helium in MRI magnets, magnesium diboride (MgB2), a high temperatur... more To reduce the usage of liquid helium in MRI magnets, magnesium diboride (MgB2), a high temperature superconductor, has been considered for use in a design of conduction cooled MRI magnets. Compared to NbTi wires the normal zone propagation velocity (NZPV) in MgB2 is much slower leading to a higher temperature rise and the necessity of active quench protection. The temperature rise, resistive voltage, and NZPV during a quench in a 1.5 T main magnet design with MgB2 superconducting wire was calculated for a variety of wire compositions. The quench development was modeled using the Douglas–Gunn method to solve the 3D heat equation. It was determined that wires with higher bulk thermal conductivity and lower electrical resistivity reduced the hot-spot temperature rise near the beginning of a quench. These improvements can be accomplished by increasing the copper fraction inside the wire, using a sheath material (such as Glidcop) with a higher thermal conductivity and lower electrical re...
ABSTRACT The influence of Ti on phase formation in both rod-in-tube (RIT) and ``tube-type&#39... more ABSTRACT The influence of Ti on phase formation in both rod-in-tube (RIT) and ``tube-type'' Nb3Sn strands has been explored. Two RIT subelement billets and three tube-type subelements were prepared. In one of the RIT subelements and one of the tube-type subelements the Sn source was alloyed with Ti, otherwise the core was of unalloyed Sn. After drawing to final size the strands were reacted according to a typical schedule consisting of: (i) ramp at 10°C/h to 185°C, hold 24 h, (ii) ramp at 25°C/h to 340°C, hold 48 h, (iii) ramp at 10°C/h to 650°C, hold to various times. After a sequenced of holding times, the samples were quenched to retain the high temperature phases, enabling the formation of the various Nb-, Cu-, Sn-, Ta-, and Ti-containing phases to be studied by SEM and EDS. The results were compared with predictions based on the Cu-Sn and Nb-Cu-Sn phase diagrams.
IEEE Transactions on Applied Superconductivity, 2019
The critical current density at 4.2 and 20 K up to 15 T and the temperature dependence of the irr... more The critical current density at 4.2 and 20 K up to 15 T and the temperature dependence of the irreversible field have been studied in magnesium diboride wires and bulks prepared from boron without and with carbon addition. Structural investigations using X-ray microprobe analysis have been performed. A monofilamentary wire with a round-shaped core manufactured from boron containing 2 mol.% carbon (approximate composition of its matrix MgB<sub>1.8–2.4</sub>O<sub>0.04–0.71</sub>C<sub>0.12–0.16</sub>) demonstrated <italic>J</italic><sub>c</sub>(20 K, 2 T) = 10<sup>5</sup> A/cm<sup>2</sup>, <italic>J</italic><sub>c</sub>(4.2 K, 15 T) = 2 × 10<sup>3</sup> A/сm <sup>2</sup> and <italic>B</italic><sub>irr</sub> (20 K) = 8 T, <italic>B</italic><sub>irr</sub>(12.5 K) = 15 T. Bulk material synthesized at 2 GPa, 600 °C, 1 h from carbon doped boron demonstrated <italic>J</italic><sub>c</sub>(10 K, 10 T) = 4 × 10<sup>3</sup> A/сm <sup>2</sup> and <italic>J</italic><sub>c</sub>(20 K, 6 T) = 4 × 10<sup>3</sup> A/сm <sup>2</sup>.
An efficient cooling system and the superconducting magnet are essential components of magnetic r... more An efficient cooling system and the superconducting magnet are essential components of magnetic resonance imaging (MRI) technology. Herein, we report a solid nitrogen (SN2) cooling system as a valuable cryogenic feature, which is targeted for easy usability and stable operation under unreliable power source conditions, in conjunction with a magnesium diboride (MgB2) superconducting magnet. The rationally designed MgB2/SN2 cooling system was first considered by conducting a finite element analysis simulation, and then a demonstrator coil was empirically tested under the same conditions. In the SN2 cooling system design, a wide temperature distribution on the SN2 chamber was observed due to the low thermal conductivity of the stainless steel components. To overcome this temperature distribution, a copper flange was introduced to enhance the temperature uniformity of the SN2 chamber. In the coil testing, an operating current as high as 200 A was applied at 28 K (below the critical curr...
Coupled magneto-optical imaging and local misorientation angle mapping have been used to demonstr... more Coupled magneto-optical imaging and local misorientation angle mapping have been used to demonstrate the percolative nature of supercurrent flow in YBa2Cu3O7−x(YBCO) coated conductors grown on deformation-textured Ni substrates. Barriers to current flow occur at many YBCO grain boundaries (GBs) which have propagated through the buffer layers from the underlying Ni substrate, and all Ni GBs with misorientation angles >4° initiate percolative current flow. This type of current barrier is characteristic of the conductor form and has been found to exist in samples with Jc(0 T,77 K) values >2 MA/cm2. Sharpening of the local substrate texture or improving in low-angle GB properties should lead to higher Jc values.
ABSTRACT Increasing the pressure during manufacturing MgB2 enhances the volume pinning force and ... more ABSTRACT Increasing the pressure during manufacturing MgB2 enhances the volume pinning force and moves the position of the maximum to higher magnetic fields. A similar shift was observed when Ti or SiC was added and the maximum of the volume pinning force was found at higher fields in in situ synthesized materials than in ex situ sintered samples. We attribute the observed changes to Mg–B–O oxygen-enriched regions and grains of higher magnesium borides in the MgB2 matrix. High-temperature processed materials demonstrated mainly point or mixed pinning while grain boundary pinning dominated after low-temperature synthesis.
ABSTRACT Structures of MgB2-based materials manufactured under pressure (up to 2 GPa) by differen... more ABSTRACT Structures of MgB2-based materials manufactured under pressure (up to 2 GPa) by different methods having high superconducting performance and connectivity are multiphase and contain different Mg-B-O compounds. Some oxygen can be incorporated into MgB2 and boron into MgO structures, MgBx (X=4-20) inclusions contain practically no oxygen. Regulating manufacturing temperature, pressure, introducing additions one can influence oxygen and boron distribution in the materials and thus, affect the formation, amount and sizes of Mg-B-O and MgBx inclusions and changing type of pinning, pinning force and so affect critical current density j(c). The boron concentration increase in initial Mg and B mixture allows obtaining sample containing 88.5 wt% of MgB12 with T-C of 37.4 K (estimated magnetically). (C) 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of the Guest Editors.
Various MgB2 wires with different sheath materials provided by Hyper Tech Research Inc., have bee... more Various MgB2 wires with different sheath materials provided by Hyper Tech Research Inc., have been tested in the superconducting fault current limiter (SFCL) desktop tester at 24-26 K in a self-field. Samples 1 and 2 are similarly fabricated monofilamentary MgB2 wires with a sheath of CuNi, except that sample 2 is doped with SiC and Mg addition. Sample 3 is
International Journal of Applied Ceramic Technology, 2007
Since 2001, when magnesium diboride (MgB 2 ) was first reported to have a transition temperature ... more Since 2001, when magnesium diboride (MgB 2 ) was first reported to have a transition temperature of 39 K, conductor development has progressed to where MgB 2 superconductor wire in kilometer-long piece-lengths has been demonstrated in coil form. Now that the wire is ...
IEEE Transactions on Appiled Superconductivity, 2000
Polycrystalline Ni has been used as a substrate for high-current, coated YBa2Cu3Ox superconductor... more Polycrystalline Ni has been used as a substrate for high-current, coated YBa2Cu3Ox superconductors. For many conductors, Ni is rolled to large deformation and annealed to produce a cube texture. In this study, Ni was rolled to &amp;amp;amp;amp;amp;amp;gt;95% reduction and annealed in 5% H2/95% He at 300-1000°C for various times. The resulting substrates were examined by scanning electron microscopy, X-ray and
L'invention concerne un dispositif et un procede pour la formation continue de fil supracondu... more L'invention concerne un dispositif et un procede pour la formation continue de fil supraconducteur et les produits fabriques a partir du fil. Le procede peut comprendre la fourniture d'au moins une bande de revetement metallique continue et au moins une forme metallique, formant en continu une bande de revetement metallique continue pour former une configuration partiellement ouverte, remplissant en continu la configuration partiellement ouverte de precurseur a base de diborure de magnesium comprenant du bore, et une forme metallique, et fermant la configuration partiellement ouverte, enfermant ainsi le precurseur a base de diborure de magnesium comprenant du bore, et une forme metallique, pour former une configuration fermee. Une reduction ulterieure du diametre et un allongement de la longueur de la configuration fermee, suivies d'un traitement thermique, catalysent la transformation du precurseur a base de diborure de magnesium comprenant du bore, et la forme metalliq...
To reduce the usage of liquid helium in MRI magnets, magnesium diboride (MgB2), a high temperatur... more To reduce the usage of liquid helium in MRI magnets, magnesium diboride (MgB2), a high temperature superconductor, has been considered for use in a design of conduction cooled MRI magnets. Compared to NbTi wires the normal zone propagation velocity (NZPV) in MgB2 is much slower leading to a higher temperature rise and the necessity of active quench protection. The temperature rise, resistive voltage, and NZPV during a quench in a 1.5 T main magnet design with MgB2 superconducting wire was calculated for a variety of wire compositions. The quench development was modeled using the Douglas–Gunn method to solve the 3D heat equation. It was determined that wires with higher bulk thermal conductivity and lower electrical resistivity reduced the hot-spot temperature rise near the beginning of a quench. These improvements can be accomplished by increasing the copper fraction inside the wire, using a sheath material (such as Glidcop) with a higher thermal conductivity and lower electrical re...
ABSTRACT The influence of Ti on phase formation in both rod-in-tube (RIT) and ``tube-type&#39... more ABSTRACT The influence of Ti on phase formation in both rod-in-tube (RIT) and ``tube-type&#39;&#39; Nb3Sn strands has been explored. Two RIT subelement billets and three tube-type subelements were prepared. In one of the RIT subelements and one of the tube-type subelements the Sn source was alloyed with Ti, otherwise the core was of unalloyed Sn. After drawing to final size the strands were reacted according to a typical schedule consisting of: (i) ramp at 10°C/h to 185°C, hold 24 h, (ii) ramp at 25°C/h to 340°C, hold 48 h, (iii) ramp at 10°C/h to 650°C, hold to various times. After a sequenced of holding times, the samples were quenched to retain the high temperature phases, enabling the formation of the various Nb-, Cu-, Sn-, Ta-, and Ti-containing phases to be studied by SEM and EDS. The results were compared with predictions based on the Cu-Sn and Nb-Cu-Sn phase diagrams.
IEEE Transactions on Applied Superconductivity, 2019
The critical current density at 4.2 and 20 K up to 15 T and the temperature dependence of the irr... more The critical current density at 4.2 and 20 K up to 15 T and the temperature dependence of the irreversible field have been studied in magnesium diboride wires and bulks prepared from boron without and with carbon addition. Structural investigations using X-ray microprobe analysis have been performed. A monofilamentary wire with a round-shaped core manufactured from boron containing 2 mol.% carbon (approximate composition of its matrix MgB<sub>1.8–2.4</sub>O<sub>0.04–0.71</sub>C<sub>0.12–0.16</sub>) demonstrated <italic>J</italic><sub>c</sub>(20 K, 2 T) = 10<sup>5</sup> A/cm<sup>2</sup>, <italic>J</italic><sub>c</sub>(4.2 K, 15 T) = 2 × 10<sup>3</sup> A/сm <sup>2</sup> and <italic>B</italic><sub>irr</sub> (20 K) = 8 T, <italic>B</italic><sub>irr</sub>(12.5 K) = 15 T. Bulk material synthesized at 2 GPa, 600 °C, 1 h from carbon doped boron demonstrated <italic>J</italic><sub>c</sub>(10 K, 10 T) = 4 × 10<sup>3</sup> A/сm <sup>2</sup> and <italic>J</italic><sub>c</sub>(20 K, 6 T) = 4 × 10<sup>3</sup> A/сm <sup>2</sup>.
An efficient cooling system and the superconducting magnet are essential components of magnetic r... more An efficient cooling system and the superconducting magnet are essential components of magnetic resonance imaging (MRI) technology. Herein, we report a solid nitrogen (SN2) cooling system as a valuable cryogenic feature, which is targeted for easy usability and stable operation under unreliable power source conditions, in conjunction with a magnesium diboride (MgB2) superconducting magnet. The rationally designed MgB2/SN2 cooling system was first considered by conducting a finite element analysis simulation, and then a demonstrator coil was empirically tested under the same conditions. In the SN2 cooling system design, a wide temperature distribution on the SN2 chamber was observed due to the low thermal conductivity of the stainless steel components. To overcome this temperature distribution, a copper flange was introduced to enhance the temperature uniformity of the SN2 chamber. In the coil testing, an operating current as high as 200 A was applied at 28 K (below the critical curr...
Coupled magneto-optical imaging and local misorientation angle mapping have been used to demonstr... more Coupled magneto-optical imaging and local misorientation angle mapping have been used to demonstrate the percolative nature of supercurrent flow in YBa2Cu3O7−x(YBCO) coated conductors grown on deformation-textured Ni substrates. Barriers to current flow occur at many YBCO grain boundaries (GBs) which have propagated through the buffer layers from the underlying Ni substrate, and all Ni GBs with misorientation angles >4° initiate percolative current flow. This type of current barrier is characteristic of the conductor form and has been found to exist in samples with Jc(0 T,77 K) values >2 MA/cm2. Sharpening of the local substrate texture or improving in low-angle GB properties should lead to higher Jc values.
ABSTRACT Increasing the pressure during manufacturing MgB2 enhances the volume pinning force and ... more ABSTRACT Increasing the pressure during manufacturing MgB2 enhances the volume pinning force and moves the position of the maximum to higher magnetic fields. A similar shift was observed when Ti or SiC was added and the maximum of the volume pinning force was found at higher fields in in situ synthesized materials than in ex situ sintered samples. We attribute the observed changes to Mg–B–O oxygen-enriched regions and grains of higher magnesium borides in the MgB2 matrix. High-temperature processed materials demonstrated mainly point or mixed pinning while grain boundary pinning dominated after low-temperature synthesis.
ABSTRACT Structures of MgB2-based materials manufactured under pressure (up to 2 GPa) by differen... more ABSTRACT Structures of MgB2-based materials manufactured under pressure (up to 2 GPa) by different methods having high superconducting performance and connectivity are multiphase and contain different Mg-B-O compounds. Some oxygen can be incorporated into MgB2 and boron into MgO structures, MgBx (X=4-20) inclusions contain practically no oxygen. Regulating manufacturing temperature, pressure, introducing additions one can influence oxygen and boron distribution in the materials and thus, affect the formation, amount and sizes of Mg-B-O and MgBx inclusions and changing type of pinning, pinning force and so affect critical current density j(c). The boron concentration increase in initial Mg and B mixture allows obtaining sample containing 88.5 wt% of MgB12 with T-C of 37.4 K (estimated magnetically). (C) 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of the Guest Editors.
Various MgB2 wires with different sheath materials provided by Hyper Tech Research Inc., have bee... more Various MgB2 wires with different sheath materials provided by Hyper Tech Research Inc., have been tested in the superconducting fault current limiter (SFCL) desktop tester at 24-26 K in a self-field. Samples 1 and 2 are similarly fabricated monofilamentary MgB2 wires with a sheath of CuNi, except that sample 2 is doped with SiC and Mg addition. Sample 3 is
International Journal of Applied Ceramic Technology, 2007
Since 2001, when magnesium diboride (MgB 2 ) was first reported to have a transition temperature ... more Since 2001, when magnesium diboride (MgB 2 ) was first reported to have a transition temperature of 39 K, conductor development has progressed to where MgB 2 superconductor wire in kilometer-long piece-lengths has been demonstrated in coil form. Now that the wire is ...
IEEE Transactions on Appiled Superconductivity, 2000
Polycrystalline Ni has been used as a substrate for high-current, coated YBa2Cu3Ox superconductor... more Polycrystalline Ni has been used as a substrate for high-current, coated YBa2Cu3Ox superconductors. For many conductors, Ni is rolled to large deformation and annealed to produce a cube texture. In this study, Ni was rolled to &amp;amp;amp;amp;amp;amp;gt;95% reduction and annealed in 5% H2/95% He at 300-1000°C for various times. The resulting substrates were examined by scanning electron microscopy, X-ray and
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