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Hubertus W. Weijers

Bio: Hubertus W. Weijers is an academic researcher from Florida State University. The author has contributed to research in topics: Electromagnetic coil & Superconducting magnet. The author has an hindex of 24, co-authored 99 publications receiving 2477 citations. Previous affiliations of Hubertus W. Weijers include Victoria University of Wellington & University of Twente.


Papers
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Journal ArticleDOI
TL;DR: In this article, the design and fabrication of a 32 T, 32 mm cold bore superconducting magnet with high field REBCO inner coils is underway at the NHMFL.
Abstract: The design and fabrication of a 32 T, 32 mm cold bore superconducting magnet with high field REBCO inner coils is underway at the NHMFL. In support of the design, conductor characterization measurements have been made including critical current as a function of field, field orientation, temperature, and strain on conductors and joints. Various conductor and turn insulation systems were examined. The selected coil fabrication method for the 32 T magnet is pancake wind, dry wind coils with sol-gel insulation on a stainless steel co-wind. Quench protection of the REBCO coils by distributed heaters is under development. Small REBCO coils have been made and tested in a 20 T background field to demonstrate performance of the technology. The design of the 32 T magnet is described, including coil configuration and conductor lengths, fraction of critical current, selection of conductor copper content for protection, and stress in the windings.

194 citations

Journal ArticleDOI
TL;DR: In this article, the NHMFL developed high-field magnet technology based on both YBCO-coated tape conductors and Bi-2212 round wires, which achieved state-of-the-art performance.
Abstract: Development of high-field magnets using high temperature superconductors (HTS) is a core activity at the NHMFL. Magnet technology based on both YBCO-coated tape conductors and Bi-2212 round wires is being pursued. Two specific projects are underway. The first is a user magnet with a 17 T YBCO coil set which, inside an LTS outsert, will generate a combined field of 32 T. The second is a 7 T Bi2212 demonstration coil set to be operated in a large bore resistive magnet to generate a combined magnetic field of 25 T. Owing to the substantial technological differences of the two conductor types, each project faces different conductor and magnet technology challenges. Two small coils have been tested in a 38-mm cold bore cryostat inserted in a 31 T resistive magnet: a Bi2212 round-wire layer-wound insert coil that generated 1.1 T for a total of 32.1 T and a YBCO double-pancake insert that generated 2.8 T for a total central field of 33.8 T. Four larger layer-wound coils have been manufactured and tested in a 20 T, 186-mm cold bore resistive magnet: a sizeable Bi-2212 coil and three thin large-diameter YBCO coils. The test results are discussed. The current densities and stress levels that these coils tolerate underpin our conviction that >30 T all-superconducting magnets are viable.

178 citations

Journal ArticleDOI
TL;DR: In this article, the ability of 2G HTS wire to operate under high stress levels has been demonstrated in both direct sample measurement and test coils, and the high winding current density that is available with SuperPower's thin 2GHTS wire was utilized in a high field insert coil demonstration generating central fields in excess of 26.8 T.
Abstract: Recent developments in 2G HTS coil technology are presented highlighting the ability of 2G HTS wire to function under difficult operating conditions without degradation. The challenges of use in various coil constructions and applications are discussed. Several applications where the conductor is subjected to high stress levels include high field insert coils and rotating machinery. While these applications present different challenges, the ability of the conductor to operate under high stress levels has been demonstrated in both direct sample measurement and test coils. The high winding current density that is available with SuperPower's thin 2G HTS wire was utilized in a high field insert coil demonstration generating central fields in excess of 26.8 T . The ability of the wire to be tailored (stabilization, insulation, ac losses) to fit various operating parameters will also be discussed.

173 citations

Journal ArticleDOI
TL;DR: The 32-T superconducting magnet is envisioned as a 15-T low-temperature superconductor (LTS) magnet combined with a separately powered REBCO high temperature superconductuctor (HTS) insert configured as two coil stacks generating 17 T.
Abstract: The 32-T superconducting magnet is envisioned as a 15-T low-temperature superconductor (LTS) magnet combined with a separately powered REBCO high-temperature superconductor (HTS) insert configured as two coil stacks generating 17 T. Progress was made in all aspects of this project and is reported in this work. The design concept, which has been quite stable, is presented, as well as key elements from recent developments such as increased voltage standoff requirements. In both factory testing and installation at the NHMFL, the 15-T/250-mm-bore outer magnet built by Oxford Instruments met all specifications, including a ramp time of 1 h to full field. The test protocol included a deliberately induced full-field quench, releasing 7 MJ. After the helium level recovered, the magnet was ramped again in 1 h to full field, demonstrating full recovery. Helium boiloffs during normal operation and quench were observed, as well as the current and field decay during quench. The latter information serves as one of many inputs for the numerical quench code developed specifically to model quench in coupled LTS-HTS coils. Results from the 32-T quench analysis and implications for quench protection are summarized. All HTS conductor lengths were subjected to an extensive quality assurance (QA) protocol, and SuperPower has now delivered all required conductor lengths within specifications. A summary of the QA data and its implications are presented. The prototype coils, which are very similar in design to the 32-T REBCO coils but of reduced height, have now been impregnated with paraffin to address winding motion observed in previous testing. The prototype test protocol includes a study of the effectiveness of the quench heaters in the HTS coils in both a constant background field as provided by the actual 15-T LTS outer magnet for 32 T and, uniquely, in case the outer magnet is deliberately quenched.

159 citations

Journal ArticleDOI
TL;DR: In this paper, present day HTS conductor and magnet technologies are discussed and a view to the future is provided, including the implementation of HTS conductors in high-field magnets, including coil manufacturing, electromechanical behavior and quench protection.
Abstract: High-field superconducting solenoids have proven themselves to be of great value to scientific research in a number of fields, including chemistry, physics and biology. Present-day magnets take advantage of the high-field properties of Nb3Sn, but the high-field limits of this conductor are nearly reached and so a new conductor and magnet technology is necessary for superconducting magnets beyond 25 T. Twenty years after the initial discovery of superconductivity at high temperatures in complex oxides, a number of high temperature superconductor (HTS) based conductors are available in sufficient lengths to develop high-field superconducting magnets. In this paper, present day HTS conductor and magnet technologies are discussed. HTS conductors have demonstrated the ability to carry very large critical current densities at magnetic fields of 45 T, and two insert coil demonstrations have surpassed the 25 T barrier. There are, however, many challenges to the implementation of HTS conductors in high-field magnets, including coil manufacturing, electromechanical behavior and quench protection. These issues are discussed and a view to the future is provided.

145 citations


Cited by
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[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal ArticleDOI
01 Jun 2019-Nature
TL;DR: A copper oxide high-temperature superconductor magnet generates a direct-current magnetic field of 45.5 tesla—the highest value reported so far—using a design that enables operation at high current densities, validates predictions11 for high-field copper oxide super Conductor magnets by achieving a field twice as high as those generated by low-tem temperature superconducting magnets.
Abstract: Strong magnetic fields are required in many fields, such as medicine (magnetic resonance imaging), pharmacy (nuclear magnetic resonance), particle accelerators (such as the Large Hadron Collider) and fusion devices (for example, the International Thermonuclear Experimental Reactor, ITER), as well as for other diverse scientific and industrial uses. For almost two decades, 45 tesla has been the highest achievable direct-current (d.c.) magnetic field; however, such a field requires the use of a 31-megawatt, 33.6-tesla resistive magnet inside 11.4-tesla low-temperature superconductor coils1, and such high-power resistive magnets are available in only a few facilities worldwide2. By contrast, superconducting magnets are widespread owing to their low power requirements. Here we report a high-temperature superconductor coil that generates a magnetic field of 14.4 tesla inside a 31.1-tesla resistive background magnet to obtain a d.c. magnetic field of 45.5 tesla—the highest field achieved so far, to our knowledge. The magnet uses a conductor tape coated with REBCO (REBa2Cu3Ox, where RE = Y, Gd) on a 30-micrometre-thick substrate3, making the coil highly compact and capable of operating at the very high winding current density of 1,260 amperes per square millimetre. Operation at such a current density is possible only because the magnet is wound without insulation4, which allows rapid and safe quenching from the superconducting to the normal state5–10. The 45.5-tesla test magnet validates predictions11 for high-field copper oxide superconductor magnets by achieving a field twice as high as those generated by low-temperature superconducting magnets. A copper oxide high-temperature superconductor magnet generates a direct-current magnetic field of 45.5 tesla—the highest value reported so far—using a design that enables operation at high current densities.

370 citations

Journal ArticleDOI
TL;DR: It is demonstrated that grain boundary limits to high Jc can be practically overcome and underlines the value of a renewed focus on grain boundary properties in non-ideal geometries.
Abstract: Cuprate superconductors have found limited application for high-field magnets because of difficulties related to grain boundaries. Now, this issue is partially overcome and round wires suitable for magnetic coils are fabricated from Bi2Sr2CaCu2O8−x.

302 citations

Journal ArticleDOI
TL;DR: In this article, the feasibility of high field magnet applications of the twisted stacked-tape cabling method with 2G YBCO tapes has been investigated, taking into account the internal shortening compressive strains accompanied with the lengthening tensile strains due to the torsional twist.
Abstract: The feasibility of high field magnet applications of the twisted stacked-tape cabling method with 2G YBCO tapes has been investigated. An analysis of torsional twist strains of a thin HTS tape has been carried out taking into account the internal shortening compressive strains accompanied with the lengthening tensile strains due to the torsional twist. The model is benchmarked against experimental tests using YBCO tapes. The critical current degradation and current distribution of a four-tape conductor was evaluated by taking account of the twist strain, the self-field and the termination resistances. The critical current degradation for the tested YBCO cables can be explained by the perpendicular self-field effect. It is shown that the critical current of a twisted stacked-tape conductor with a four-tape cable does not degrade with a twist pitch length as short as 120 mm. Current distribution among tapes and hysteresis losses are also investigated. A compact joint termination method for a 2G YBCO tape cable has been developed. The twisted stacked-tape conductor method may be an attractive means for the fabrication of highly compact, high current cables from multiple flat HTS tapes.

302 citations