The effect of the wire design parameters on the stability of MgB 2 superconducting coils

The study of the stability process of MgB 2 superconducting wires and coils is an important issue in the design and feasibility of electric power applications. In this sense, the thermal conductivity plays an important role, which in composite wires and tapes is mainly determined by the amount of stabilizer (usually copper), the configuration of filaments and the metallic matrix; while for coils, the winding, wire electric insulation

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental and numerical analysis of quench propagation on MgB₂tapes and pancake coils

Pelegrin¹,

Romano²,

Martínez³

et al. 2013

“…The NZPV decreases when comparing one-dimensional wire cases with wire wound in a two or three-dimensional coil [64–66]. Numeric simulations show that the increase in copper fraction does not really effect or slightly increases the NZPV provided that the superconductor fraction and cross-sectional area of the bare wire remains constant [39, 69]. When the Monel sheath is replaced by Glidcop while the cross-sectional area and the fraction of copper, MgB 2 and niobium remain constant, numeric simulations show little change in the NZPV [39].…”

Section: Thermal Properties and Quench Propagation Of Mgb2 Coilsmentioning

confidence: 99%

“…However, experiments have shown that a Glidcop sheathed wire has a slightly decreased NZPV compared to a Monel sheathed wire [63]. Numeric simulations show that the increase in copper fraction inside the wire slightly increases the NZPV [39, 69]. …”

Section: Thermal Properties and Quench Propagation Of Mgb2 Coilsmentioning

confidence: 99%

Conceptual designs of conduction cooled MgB₂ magnets for 1.5 and 3.0 T full body MRI systems

Baig

Amin

Deissler

et al. 2017

Conceptual designs of 1.5 and 3.0 T full-body magnetic resonance imaging (MRI) magnets using conduction cooled MgB2 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. MgB2 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 MgB2. A new ‘active’ protection scheme for medium Tc based MRI magnets is presented and simulations demonstrate that the magnet can be protected. Recent progress on persistent joints for multifilamentary MgB2 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 MgB2 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 MgB2 magnet designs.

“…Thus, the energy required to initiate a quench in a NbTi coil is very small, and the coils are fairly sensitive to the energy released by epoxy cracking, or wire movement. MgB 2 has a significantly higher MQE, typically ranging from 1 to 10 J [31][32][33][34][35][36][37][38][39][40][41][42][43]. Numerical [27,34,44] and experimental [35][36][37][38] studies on the quench behavior of conduction-cooled MgB 2 coils and short samples have been performed by many groups.…”

Section: Introductionmentioning

confidence: 99%

Quench, normal zone propagation velocity, and the development of an active protection scheme for a conduction cooled, react-and-wind, MgB₂ MRI coil segment

Zhang

Sumption

Majoroš

et al. 2019

The development of coils that can survive a quench is crucial for demonstrating the viability of MgB2-based main magnet coils used in MRI systems. Here we have studied the performance and quench properties of a large (outer diameter: 901 mm; winding pack: 44 mm thick × 50.6 mm high) conduction-cooled, react-and-wind, MgB2 superconducting coil. Minimum quench energy (MQE) values were measured at several coil operating currents (Iop), and distinguished from the minimum energy needed to generate a normal zone (MGE). During these measurements, normal zone propagation velocities (NZPV) were also determined using multiple voltage taps placed around the heater zone. The conduction cooled coil obtained a critical current (Ic) of 186 A at 15 K. As the operating currents (Iop) varied from 80 to 175 A, MQE ranged from 152 to 10 J, and NZPV increased from 1.3 to 5.5 cm s−1. Two kinds of heater were involved in this study: (1) a localized heater (‘test heater’) used to initiate the quench, and (2) a larger ‘protection heater’ used to protect the coil by distributing the normal zone after a quench was detected. The protection heater was placed on the outside surface of the coil winding. The test heater was also placed on the outside surface of the coil at a small opening made in the protection heater. As part of this work, we also developed and tested an active protection scheme for the coil. Such active protection schemes are of great interest for MgB2-based MRIs because they permit exploitation of the relatively large MQE values of MgB2 to enable the use of higher Je values which in turn lead to competitive MgB2 MRI designs. Finally, the ability to use a quench detection voltage to fire a protection heater as part of an active protection scheme was also demonstrated.