1.5T cryogen free superconducting magnet for dedicated MRI

Рыбаков, А. С.; Bagdinov, A. V.; Демихов, Е. И.; Kostrov, E. A.; Лысенко, В. В.; Piskunov, Nikolay; Tysyachnykh, Yuriy

doi:10.1109/tasc.2016.2517328

Cited by 13 publications

(6 citation statements)

References 6 publications

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“…The basic cooling strategy for this 14 T HTS magnet is like most of other conduction-cooled magnets [20,26,[45][46][47][48]: as introduced in section 2, there is a copper sheet between every two pancakes of a DP unit; the coils will be cooled by the copper sheets, through flexible oxygen-free copper strands [20,48], and to the 2nd stage of the cold head (multiple copper strands will connect DP copper sheets at the coils end and gather onto the cold head end); to reduce the thermal radiation into the coils, an aluminum thermal shield is employed and connected to the 1st stage of the cold head; multi-layer insulation is attached on the outer surface of the thermal shield for radiation reduction on the thermal shield.…”

Section: Cooling Strategymentioning

confidence: 99%

Key designs of a short-bore and cryogen-free high temperature superconducting magnet system for 14 T whole-body MRI

Roell

2021

Supercond. Sci. Technol.

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A 14 T whole-body magnetic resonance imaging (MRI) magnet is designed with Bi2223 high temperature superconducting (HTS) wire. Owing to the large critical current and large critical tensile strength of the wire type HT-NX at ultra-high field, the magnet is optimized in a compact shape with length of 1.9 m and outer diameter of 1.3 m. It is in the form of stacked double pancakes (DPs) with total wire consumption of 455 km. The DPs with various inner and outer radii enable the electromagnetic design to obtain highly homogeneous field of 1.5 ppm over 400 mm diameter of spherical volume (DSV). Hoopstress by winding process, thermal contraction and Lorenz force is calculated and below the wire strength specification. Considerable reduction of screening current effect in MRI magnet application is proved by a calculation example. Field homogeneity as it is influenced by various systematic tolerances and random geometric tolerances is numerically estimated, for further design optimization and design of shimming system. Iron room for passive shielding with dimension of 5 × 5 × 10 m is found to be with wall thickness of around 30 cm to effectively contain the 5-Gauss field to the wall surface. Cooling strategy for cryogen-free technique is proposed and the magnet coils temperature is calculated as below 8 K based on the estimation of joint Ohmic heating power of 1.0 W. Quench protection adopts circuit subdivision and dumping resistors to restrict the maximum voltage below 1.9 kV. No-insulation technique for the quench protection is also discussed. Some other wire candidates like REBCO and Nb3Sn for development of such ultra-high field MRI magnets are commented.

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Section: Cooling Strategymentioning

confidence: 99%

Key designs of a short-bore and cryogen-free high temperature superconducting magnet system for 14 T whole-body MRI

Roell

2021

Supercond. Sci. Technol.

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“…Conduction cooling of superconducting magnets for MRI systems has already been considered in previous work [40, 41] and has been explored for a wide range of superconducting material and magnet designs [7–9, 11, 24, 42–44], and is considered for our design. The goal is to eliminate the need for LHe bath cooling, which would benefit the MRI magnet industry by decoupling the magnets from any instability in the LHe market.…”

Section: Conduction Coolingmentioning

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

Supercond. Sci. Technol.

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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.

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“…The magnetic field homogeneity should be better than 0.1 ppm over a 5 mm DSV. The NMR magnet will operate at liquid helium at 4.2 K. To reduce the refill helium routinely and reduce the vibration during operation, a pulsed tube refrigerator (PTR) will be used [8]- [10]. The magnet needs to be operated in a persistent mode to limit magnetic field decay by using the superconducting joint.…”

Section: Introductionmentioning

confidence: 99%

Design of a 9.4 T Superconducting Magnet for 400 MHz Nuclear Magnetic Resonance

Ren¹,

Li²,

Chen³

2022

Preprint

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A 9.4 T/400 MHz superconducting magnet with a warm bore of 60 mm is being designed. The 400 MHz NMR magnet is composed of 9 coaxial coils to generate a central field of 9.4 T. The magnetic field homogeneity is better than 4 ppm for 50 mm diameter spherical volume (DSV) and better than 1 ppb for 5 mm DSV. Three types of NbTi strands were used to reduce the cost of the superconducting materials. A preload with 80 MPa was exerted on the superconducting coils and over-banding with stainless steel was adopted to release the stress from the electromagnetic forces. The magnet will be operated in persistent mode with superconducting joints to reduce the field decay. The pulse tube cryocooler with a cooling capacity of 1 W at 4.2 K can be used to reduce the liquid helium evaporation and vibration during operation. The magnet will be equipped with Bi2223/AgAu HTS current leads to reduce the heat losses. In this paper, the design of the 9.4 T NMR superconducting coils, electromagnetic field calculations, and stress analysis of the superconducting coils were presented.

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1.5T cryogen free superconducting magnet for dedicated MRI

Cited by 13 publications

References 6 publications

Key designs of a short-bore and cryogen-free high temperature superconducting magnet system for 14 T whole-body MRI

Key designs of a short-bore and cryogen-free high temperature superconducting magnet system for 14 T whole-body MRI

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

Design of a 9.4 T Superconducting Magnet for 400 MHz Nuclear Magnetic Resonance

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1.5T cryogen free superconducting magnet for dedicated MRI

Cited by 13 publications

References 6 publications

Key designs of a short-bore and cryogen-free high temperature superconducting magnet system for 14 T whole-body MRI

Key designs of a short-bore and cryogen-free high temperature superconducting magnet system for 14 T whole-body MRI

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

Design of a 9.4 T Superconducting Magnet for 400 MHz Nuclear Magnetic Resonance

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