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

Abstract

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.

Pinning behavior in bulk MgB2 prepared using boron powder refined via high-energy ultra-sonication

“…Due to uniform trapped field, and cheap and simple processing, MgB 2 is suitable for several superconductor applications such as bulk magnets for compact MRI and NMR, electric motors, etc. [2][3][4]. Furthermore, its light weight is an important feature that might be crucial for some applications, especially space ones [5].…”

Development of Prototype MGB 2 Superconducting Solenoid Magnet for High-Efficiency Klystron Applications

“…As for MgB2 coils, D. Zhang et al successfully made a coil by using a react-and-wind method with 1.7 km of conductor, that was 900 mm in diameter; the operation point of the coil was 200 A at 13 K and 1.93 T [6]. A magnet using this coil will be protected by active quench protection with heaters [7]. This paper describes a coil and magnet design fulfilling the above requirements for energy saving and passive quench protection and the test results of a preliminary experimental coil, a pair of prototype coils (before assembling), and a prototype magnet after assembling with the cryostat also functioning the magnetic flux return yoke.…”

A new remote monitoring device to track magnetic resonance imaging machine cooling system failures

“…To accomplish that liquid helium is used, which is cooled using a specialized compressor called a Cryo-chiller. There are many series of coils and heat exchangers that are used to cool the cryo-cooler, which is crucial because if the helium temperature increases, the machine may overheat, without cooling, within a few hours, all the helium will vaporize and escape through the safety valves, after which the magnet will suffer irreparable damage [11]- [15]. Helium refills cost tens of thousands of dollars, while the loss of the magnet can push the capital loss to several million.…”