Development of a superconducting bulk magnet for NMR and MRI

Nakamura, Takashi; Tamada, Daiki; Yanagi, Yousuke; Itoh, Yoshitaka; Nemoto, Takahiro; Utumi, Hiroaki; Kose, Katsumi

doi:10.1016/j.jmr.2015.07.012

Cited by 108 publications

(73 citation statements)

References 22 publications

(29 reference statements)

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“…As a result, a 400 MHz (9.4 T) NMR bulk magnet can be realised without fracture [15]. (5) The mechanical strain has been directly measured on a ring bulk surface during the cooling process and FCM using a strain gauge, verifying that the simulation results qualitatively reproduce the experimental results [16].…”

Section: Introductionmentioning

confidence: 63%

Promising effects of a new hat structure and double metal ring for mechanical reinforcement of a REBaCuO ring-shaped bulk during field-cooled magnetisation at 10 T without fracture

Fujishiro¹,

Naito²,

Yanagi³

et al. 2019

Supercond. Sci. Technol.

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PAPERPromising effects of a new hat structure and double metal ring for mechanical reinforcement of a REBaCuO ring-shaped bulk during fieldcooled magnetisation at 10 T without fracture AbstractWe have investigated a new reinforcement hat structure for a RE-Ba-Cu-O (REBaCuO, RE: rare earth element or Y) ring-shaped bulk superconductor (ring bulk) shrink-fitted with a double Al alloy ring and set on the cold stage of a cryogenic refrigerator prior to field-cooled magnetisation (FCM). With the hat structure, a ring bulk having an outer diameter of 64 mm, inner diameter of 40 mm, and height of 20.5 mm achieved a trapped field as high as 6.8 T at 50 K during FCM with an applied magnetic field at B app =10 T without fracture; a similar ring bulk without the hat structure broke during FCM at B app =8.8 T. Using a numerical simulation for electromagnetic and mechanical properties, the potential benefit of the hat structure was confirmed. The magnetic field dependence of the average critical current density J c (B) of the ring bulk used in the simulation was determined by experimental results of time step dependence of the trapped field B z at the bulk centre. As a result, the total hoop stress σ θ total in the ring bulk including the resulting stress of cooling from 300 K to 50 K and subsequent FCM at B app =10 T is lower than the fracture strength of a typical Ag-doped REBaCuO bulk material. The effect of double Al alloy ring reinforcement was also analysed using a numerical simulation and compared with that of the conventional single Al alloy ring reinforcement. These results suggest that the double ring provides only a limited benefit, whereas the hat structure is fairly effective in reducing the electromagnetic hoop stress during FCM at B app =10 T. Using this reinforcement method, a 400 MHz (9.4 T) nuclear magnetic resonance bulk magnet system could be realised.

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Section: Introductionmentioning

confidence: 63%

Promising effects of a new hat structure and double metal ring for mechanical reinforcement of a REBaCuO ring-shaped bulk during field-cooled magnetisation at 10 T without fracture

Fujishiro¹,

Naito²,

Yanagi³

et al. 2019

Supercond. Sci. Technol.

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“…Akin to YBa 2 Cu 3 O 7‐δ (YBCO) and (Rare‐Earth)Ba 2 Cu 3 O 7 (REBCO) cryomagnets, 8,9 bulk MgB 2 could be used for various applications such as the delivery of drug at specified locations in the human body using an external magnetic force, 10 magnetic separation systems, 11 portable nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) devices, 12 generators or motors 13,14 etc… For all these applications, the trapped magnetic field of present MgB 2 bulks must be improved. According to the Bean model, the trapped field is proportional to the critical current density, J c , and depends on the size of the persistent current loops, 15 that is linked to the sample size.…”

Section: Introductionmentioning

confidence: 99%

Improvement of critical current density of MgB₂ bulk superconductor processed by Spark Plasma Sintering

et al. 2020

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Spark Plasma Sintering (SPS) is a promising rapid consolidation technique that allows a better understanding and optimization of the sintering kinetics and therefore makes it possible to obtain MgB2 bulk superconductor with tailored microstructures consisting of grains with either spherical or elongated morphology. In this contribution, the role of the precursor powders on the superconducting properties of MgB2 is investigated. Three sets of bulk MgB2 material were processed from: (i) a commercially available MgB2 powder; (ii) a mixture of Mg metal and amorphous B using a single‐step solid‐state reaction process and (iii) a mixture of amorphous boron coated with carbon and Mg metal. The samples were prepared in the same SPS processing conditions. The microstructure of the samples was investigated by X‐ray diffraction, SEM and TEM and correlated to their superconducting properties. The critical current density of the best sample at 20K was Jc = 500 kA/cm2 in self‐field, which is one of the highest critical current density reported for MgB2 bulk superconductors.

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“…To address these issues and to achieve record trapped fields of over 17 T, bulk superconducting samples have been reinforced by various techniques, including resin and alloy impregnation, carbon fiber wrapping [4] and shrink-fit stainless steel rings [5]. It is clear, therefore, that adequate mechanical reinforcement and thermal stability are key to achieving a trapped field greater than 20 T, which, in turn, could strengthen the case for practical applications such as compact nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) systems, magnetic separation and magnetically targeted drug delivery [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Composite stacks for reliable > 17 T trapped fields in bulk superconductor magnets

Huang

Shi

Srpcic

et al. 2019

Supercond. Sci. Technol.

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Trapped fields of over 20 T are, in principle, achievable in bulk, single-grain high temperature cuprate superconductors. The principle barriers to realizing such performance are, firstly, the large tensile stresses that develop during the magnetization of such trapped-field magnets as a result of the Lorentz force, which lead to brittle fracture of these ceramic-like materials at high fields and, secondly, catastrophic thermal instabilities as a result of flux movement during magnetization. Moreover, for a batch of samples nominally fabricated identically, the statistical nature of the failure mechanism means the best performance (i.e. trapped fields of over 17 T) cannot be attained reliably. The magnetization process, particularly to higher fields, also often damages the samples such that they cannot repeatedly trap high fields following subsequent magnetization. In this study, we report the sequential trapping of magnetic fields of ~ 17 T, achieving 16.8 T at 26 K initially and 17.6 T at 22.5 K subsequently, in a stack of two Ag-doped GdBa2Cu3O7-δ bulk superconductor composites of diameter 24 mm reinforced with (1) stainless-steel laminations, and (2) shrink-fit stainless steel rings. A trapped field of 17.6 T is, in fact, comparable with the highest trapped fields reported to date for bulk superconducting magnets of any mechanical and chemical composition, and this was achieved using the first composite stack to be fabricated by this technique. These post-meltprocessing treatments, which are relatively straightforward to implement, were used to improve both the mechanical properties and the thermal stability of the resultant composite structure, providing what we believe is a promising route to achieving reliably fields of over 20 T.

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Development of a superconducting bulk magnet for NMR and MRI

Cited by 108 publications

References 22 publications

Promising effects of a new hat structure and double metal ring for mechanical reinforcement of a REBaCuO ring-shaped bulk during field-cooled magnetisation at 10 T without fracture

Promising effects of a new hat structure and double metal ring for mechanical reinforcement of a REBaCuO ring-shaped bulk during field-cooled magnetisation at 10 T without fracture

Improvement of critical current density of MgB₂ bulk superconductor processed by Spark Plasma Sintering

Composite stacks for reliable > 17 T trapped fields in bulk superconductor magnets

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Development of a superconducting bulk magnet for NMR and MRI

Cited by 108 publications

References 22 publications

Promising effects of a new hat structure and double metal ring for mechanical reinforcement of a REBaCuO ring-shaped bulk during field-cooled magnetisation at 10 T without fracture

Promising effects of a new hat structure and double metal ring for mechanical reinforcement of a REBaCuO ring-shaped bulk during field-cooled magnetisation at 10 T without fracture

Improvement of critical current density of MgB2 bulk superconductor processed by Spark Plasma Sintering

Composite stacks for reliable > 17 T trapped fields in bulk superconductor magnets

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Product

Resources

About

Improvement of critical current density of MgB₂ bulk superconductor processed by Spark Plasma Sintering