Dry cryomagnetic system with MgB2 coil (original) (raw)
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Cryo-Free Multisection Superconducting Magnet System With MgB2Coil
IEEE Transactions on Applied Superconductivity, 2018
Comprehensive studies of the transport and the magnetic properties of MgB 2 wires were carried out at temperatures 4.2-20 K and magnetic field up to 8 T. Cryomagnetic system with MgB 2 coil was designed and constructed based on the received data. Cryomagnetic system is designed to create a permanent magnetic field of up to 5 T in the warm bore of 40 mm in diameter. The operating current of the system is 100 A. The magnetic field is created by a system of three concentric solenoids. The inner coil is composed of 10 double pancakes wound with the second generation HTS tape produced by SuperOx. Middle coil is made of multifilament MgB 2 wire with a diameter of 1 mm produced by Columbus Superconductors. Middle coil has height of 120 mm, an inner diameter of 80 mm, and an outer diameter of 88 mm. The inner and middle coils are connected in series, what allows both sections to operate at temperature range from 4.2 to 20 K. The external coil of background field is wound of NbTi. It is powered by a separate pair of current leads. The solenoids are cooled by cryocooler though copper bar. The present report describes the design and the manufacture of the cryomagnetic system.
Fusion Engineering and Design, 2015
h i g h l i g h t s • We succeeded to fabricate 100 m long MgB 2 /Ta/Cu mono-core wire and small solenoid coil for "low activation superconducting system". • From the results of the coil excitatrion test, we conclude that MgB 2 wire is an attractive alternative to NbTi for "low activation superconducting system". • J c property of the sample using 11 B isotope powder was lower than those of the samples using natural and amorphous boron powder. We thought that fine particle sized 11 B isotope powder is effective to improve J c property of the sample made by 11 B isotope.
IEEE Transactions on Applied Superconductivity, 2015
This paper presents construction and persistentmode operation results of MgB 2 coils for a 0.5-T/240-mm cold bore MRI magnet, wound-and-react with monofilament MgB 2 wire, at the MIT Francis Bitter Magnet Laboratory. The magnet, of respective inner and outer diameters of 276 and 290 mm and a total height of 460 mm, has center field of 0.5 T and current density of 11 kA/cm 2. To limit the continuous length of Hyper Tech supplied MgB 2 monofilament wire to ≤300 m, the magnet was divided into 8 series-connected coils, each equipped with a persistent current switch (PCS) and a superconducting joint. We have manufactured 3 coil modules. Before tested as an assembly, each coil was tested individually to ensure its capacity to carry 100-A superconducting current in the range 10-15 K. The 3 coils were then assembled, connected in series, and operated as a 3-coil assembly in persistent mode at nearly 100 A in the range 10-15 K. We present results that include: 1) construction details; 2) component performances; and 3) a 3-coil assembly performance.
Design Aspects on Winding of an MgB2 Superconducting Generator Coil
Energy Procedia, 2015
Generators based on superconducting rotor coils are considered for future large offshore wind turbines for their low weight and compact design, and for their possibility to reduce costs. In the 10-20 K temperature range, MgB 2 superconductors carry current densities 100 times higher than standard copper conductors at room temperature at one tenth of the wire cost per unit carried current. In the framework of the European project INNWIND.EU, an MgB 2 superconducting generator pole will be designed, built and tested. Some of the design aspects of this work with emphasis on the winding process and associated coil insulation are discussed. An overall high current density in the coil is of crucial importance to obtain clear benefits compared to conventional solutions. The wire itself may be the most important parameter in that respect. However, the overall current density of the coil is also influenced by the thickness of the turn-to-turn electrical insulation. Here we discuss the impact of the insulation and suggest the use of a one-step winding process, employing wet-winding, where the applied epoxy also constitutes the insulation layer between turns. In this way the coil is densified by approximately 10% compared to the use of an additional, dedicated, electrical insulation like Kapton for wet-winding or glass-fibre for dry-winding followed by vacuum impregnation. We show the results of a trial winding of 500 m of MgB 2 superconducting wire into a double pancake coil using the wetwinding technique. The coil is tested for contacts between the turns to evaluate the suggested one-step wet-winding process.
${\\rm MgB}_{2}$ for MRI Magnets: Test Coils and Superconducting Joints Results
IEEE Transactions on Applied Superconductivity, 2012
Among key design and operation issues for MgB 2 relevant to MRI magnets are: uniformity of current-carrying capacity over long lengths (>2 km) of wire; and reliability of a splicing technique. This paper presents experimental results of current-carrying capacities of a small test coil and joints, both made from MgB 2 round wires, multifilament and monofilament (mono), manufactured by Hyper Tech Research, Inc. The test coils were wound with 95-m long unreacted, C (carbon)doped MgB 2 multifilament wire, sintered at 700°C for 90 min. The critical currents were measured in the 4.2 K-15 K and 0 T-5 T ranges. We have modified our original splicing technique, proven successful with unreacted, un-doped MgB 2 multifilament wire sintered at
IEEE Transactions on Applied Superconductivity, 2013
This paper presents recent results from our continued development of a 0.5 T whole-body MRI magnet at the Francis Bitter Magnet Laboratory. HyperTech Research Corp. (Columbus, OH) manufactures the MgB 2 conductor for this project. During the past year, we have found that our technique, originally developed successfully to splice unreacted multifilament MgB 2 wires, works much better, i.e., of higher reliability, with unreacted monofilament MgB 2 wires. This has led us to wind the entire coil components in our persistent-mode MRI magnet with unreacted monofilament MgB 2 wire, having a MgB 2 core of 0.4 mm in diameter, an overall diameter of 0.8 mm bare, 1 mm S-glass insulated. To verify that these coils would not suffer from flux jumping, as they would if wound with monofilament NbTi wire, magnetization studies were performed on monofilament wires of MgB 2 and NbTi (as a reference) at 4.2 K. For the monofilament MgB 2 wire, the results were affirmative. To further ensure the absence of flux jumping that may quench these current-carrying coils, two test coils were wound with unreacted monofilament MgB 2 wire. One MgB 2 coil was operated in driven mode, while the other MgB 2 coil, equipped with a persistent current switch and terminated with a superconducting joint, was operated in persistent mode. The operating temperature range was 4.2-15 K for these MgB 2 coils. The driven mode coil was operated in self-field. The persistent mode coil achieved a persistent current of 100 A, corresponding to a self-field of ∼1 T in the winding, for 1 hour with no measurable decay. Both test coils were operated quench free. Index Terms-flux jumping, MgB 2 , monofilament, MRI, persistent current mode, superconducting joints.
Journal of Superconductivity and Novel Magnetism, 2020
This article presents the impact of MgB2 wire bending and diameter on transport critical current density and irreversible magnetic field of a resultant coil. Unreacted MgB2 wires 500 mm in length and 0.63 or 0.83 mm in diameter have been used in the fabrication of small diameter (14 mm) superconducting coils. The coils were subsequently annealed under isostatic pressure of 1 GPa for 15 min at 700 °C and 725 °C. Our results indicate that larger wire diameter, higher annealing temperature, and bending lead to slight reduction of critical current density and irreversible magnetic field in the coil.
Conceptual designs of conduction cooled MgB2 magnets for 1.5 and 3.0 T full body MRI systems
Superconductor Science and Technology, 2017
Conceptual designs of 1.5 and 3.0 T full-body magnetic resonance imaging (MRI) magnets using conduction cooled MgB 2 superconductor are presented. The sizes, locations, and number of turns in the eight coil bundles are determined using optimization methods that minimize the amount of superconducting wire and produce magnetic fields with an inhomogeneity of less than 10 ppm over a 45 cm diameter spherical volume. MgB 2 superconducting wire is assessed in terms of the transport, thermal, and mechanical properties for these magnet designs. Careful calculations of the normal zone propagation velocity and minimum quench energies provide support for the necessity of active quench protection instead of passive protection for medium temperature superconductors such as MgB 2. A new 'active' protection scheme for medium T c based MRI magnets is presented and simulations demonstrate that the magnet can be protected. Recent progress on persistent joints for multifilamentary MgB 2 wire is presented. Finite difference calculations of the quench propagation and temperature rise during a quench conclude that active intervention is needed to reduce the temperature rise in the coil bundles and prevent damage to the superconductor. Comprehensive multiphysics and multiscale analytical and finite element analysis of the mechanical stress and strain in the MgB 2 wire and epoxy for these designs are presented for the first time. From mechanical and thermal analysis of our designs we conclude there would be no damage to such a magnet during the manufacturing or operating stages, and that the magnet would survive various quench scenarios. This comprehensive set of magnet design considerations and analyses demonstrate the overall viability of 1.5 and 3.0 T MgB 2 magnet designs.
Demonstration of Conduction Cooled React and Wind MgB2 Coil Segment for MRI Applications
IEEE Transactions on Applied Superconductivity, 2015
This study is a contribution to the development of technology for an MgB 2 -based, cryogen-free, superconducting magnet for an MRI system. Specifically, we aim to demonstrate that a react and wind coil can be made using high performance in-situ route MgB 2 conductor, and that the conductor could be operated in conduction mode with low levels of temperature gradient. In this work, an MgB 2 conductor was used for the winding of a sub-size, MRI-like coil segment. The MgB 2 coil was wound on a 457 mm ID 101 OFE copper former using a react-and-wind approach. The total length of conductor used was 330 m. The coil was epoxy impregnated and then instrumented for low temperature testing. After the initial cool down (conduction cooling) the coil I c was measured as a function of temperature (15-30 K), and an I c of 200 A at 15 K was measured.
IEEE Transactions on Applied Superconductivity, 2008
Following a dedicated R&D program, ASG Superconductors has recently developed techniques for designing and constructing open cryogen free MRI magnets, refrigerated by two double stage cryocoolers only. The magnet consists of two coils both made with six double pancakes, each double pancake being obtained reacting and winding 1600 m of multifilamentary, copper-stabilized MgB 2 tape supplied by Columbus Superconductors. Here we report the thermal and electromagnetic characterization and the achieved targets of the first prototype, evaluated on a long term activity period. The MRI images, acquired starting from November 2006, further demonstrate the accomplishment of remarkable magnet performances. In parallel to the long term tests on the first prototype, ASG Superconductors has designed and constructed a second MRI magnet with improved characteristics. We present here the related test results and a comparison with the previous ones.