An analytical approach towards passive ferromagnetic shimming design for a high-resolution NMR magnet

Li, Frank X.; Voccio, John; Ahn, Min Cheol; Hahn, Seungyong; Bascuñán, J.; Iwasa, Y.

doi:10.1088/0953-2048/28/7/075006

Cited by 19 publications

(7 citation statements)

References 11 publications

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“…goal for our UHF NMR magnets, 1.3G and Mircro-1G, we will first minimize SCF-induced error fields by our proposed Z1 and Z2 HTS inner shim coils, then apply ferromagnetic shims, which are widely used in conventional LTS NMR 13,14 , HTS NMR 4,5,15,16 and other UHF NMR magnets 17,18 , and finally rely on room-temperature (RT) copper shim coils 19,20 for fine tuning.…”

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confidence: 99%

Prototype REBCO Z1 and Z2 shim coils for ultra high-field high-temperature superconducting NMR magnets

Park

Lee

Bascuñán

et al. 2020

Sci Rep

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We present promising results of novel high-temperature superconducting (HTS) shim coil prototypes that circumvent the size and strength limitation of our earlier innovative HTS shim concept based on 46-mm wide REBCO tape. The HTS shim coil is placed inside the HTS magnet, mainly for ultra-high-field (> 1 GHz or 23.5 T) NMR magnets, and thus unaffected from the windings’ diamagnetic wall effects. One full-scale version will be applied to clean up Z1 and Z2 harmonic errors in the MIT 1.3-GHz high-resolution NMR magnet composed of an 835-MHz HTS insert, while another version for an MIT 1-GHz microcoil NMR magnet whose small-scale model we are currently building. The prototype sets were wound with a 2-pile, 1.03-mm wide, 0.30-mm thick REBCO conductor. Operated at 77 K, the Z1 shim set generated a 1st harmonic field strength of 179 kHz/cm at 70 A, while the Z2 shim set, composed of two pairs, Z21 and Z22, generated the 2nd harmonic field of 141 kHz/cm2 at 50 A. Together with discussion on technical challenges for this REBCO shim coil concept, we demonstrate its feasibility for the next generation of ultra-high-field (UHF) HTS NMR magnets.

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confidence: 99%

Prototype REBCO Z1 and Z2 shim coils for ultra high-field high-temperature superconducting NMR magnets

Park

Lee

Bascuñán

et al. 2020

Sci Rep

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“…Such algorithms are frequently used in the context of magnetic resonance imaging (MRI) [39] in the process of shimming, which employs optimization algorithms to inform the placement of permanent magnets or current carrying wires to remove unwanted spherical harmonic contributions in a given region. These techniques for passive shimming [40] were exploited in the design of the ferromagnet array. A voxel of volume dV , magnetized entirely along z with strength M z , at a position Q = (ρ, α, ψ) produces a scalar potential at a position P = (r, θ, φ) given by,…”

Section: Magnetic Field Generationmentioning

confidence: 99%

Performance-optimized components for quantum technologies via additive manufacturing

Madkhaly,

Coles,

Morley

et al. 2021

Preprint

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Novel quantum technologies and devices place unprecedented demands on the performance of experimental components, while their widespread deployment beyond the laboratory necessitates increased robustness and fast, affordable production. We show how the use of additive manufacturing, together with mathematical optimization techniques and innovative designs, allows the production of compact, lightweight components with greatly enhanced performance. We use such components to produce a magneto-optical trap that captures ∼ 2 × 10 8 rubidium atoms, employing for this purpose a compact and highly stable device for spectroscopy and optical power distribution, optimized neodymium magnet arrays for magnetic field generation and a lightweight, additively manufactured ultra-high vacuum chamber. We show how the use of additive manufacturing enables substantial weight reduction and stability enhancement, while also illustrating the transferability of our approach to experiments and devices across the quantum technology sector and beyond.

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“…Then, field gradients by each shim are obtained. (3) The optimal thicknesses of the shim pieces at the possible positions can be calculated by means of linear programming [29,30]. The design, fabrication and installation of the three shim sets were carried out in the following sequence:…”

Section: Ferromagnetic Shimming To Improve the Homogeneity Of The 3 T...mentioning

confidence: 99%

Reproducibility of the field homogeneity of a metal-clad no-insulation all-REBCO magnet with a multi-layer ferromagnetic shim

Jang

Hwang

Han

et al. 2020

Supercond. Sci. Technol.

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We report that the field homogeneity of a large-scale metal-clad no-insulation all-ReBa 2 Cu 3 O 7−x magnet is reproducible after occasional operating conditions, in this case the current ramp down/ up and magnet warm-up/cool-down conditions. First, we shimmed the magnet by cylindrically arraying ferromagnetic shims on the wall of the room-temperature bore of the magnet to improve the spatial field homogeneity. As a result, the field homogeneity of the magnet was improved from 557.7 to 14.1 ppm in a 10 mm diameter spherical volume. The resultant acquisition of field homogeneity tremendously enhanced from an inhomogeneous state greatly degraded by screening currents qualified us to study the temporal stability of the field homogeneity. We used a magnet-energizing protocol with the field drift minimized to shrink a nuclear magnetic resonance (NMR) lineshape into a much narrower super-imposable lineshape. We demonstrate the technique by NMR experiments, showing excellent reproducibility in every case, presenting strong evidence of recovery to certain time-unvarying field gradients and to a state of homogeneity. These findings suggest a new route for high-resolution high-temperature superconducting NMR and magnetic-resonance-imaging magnet technology.

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An analytical approach towards passive ferromagnetic shimming design for a high-resolution NMR magnet

Cited by 19 publications

References 11 publications

Prototype REBCO Z1 and Z2 shim coils for ultra high-field high-temperature superconducting NMR magnets

Prototype REBCO Z1 and Z2 shim coils for ultra high-field high-temperature superconducting NMR magnets

Performance-optimized components for quantum technologies via additive manufacturing

Reproducibility of the field homogeneity of a metal-clad no-insulation all-REBCO magnet with a multi-layer ferromagnetic shim

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