An LTS/HTS NMR Magnet Operated in the Range 600–700 MHz

Bascuñán, J.; Kim, Woo Seok; Hahn, Seungyong; Bobrov, E.S.; Lee, H.; Iwasa, Y.

doi:10.1109/tasc.2007.898021

Cited by 29 publications

(24 citation statements)

References 3 publications

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“…49 The conductor J e (self) assumption required to match the model result at B A = 19 T to the measurement is in line with measured batch short sample values. However, the calculated self-field J e with axial grading exceeds the measurement by 17% and for the case without axial grading with 13%.…”

Section: Explicit Modelsupporting

confidence: 65%

“…From 2005 to 2007 the MIT team built a near replica of the above mentioned coil and operated it at 4.2 K in a 14.1 T background NMR magnet with the intent to quantify field homogeneity rather than achieving maximum central field [49]. Magnetization currents in the HTS tape conductor were found to be limiting [49,50,51].…”

Section: Brief History Of Insert Coilsmentioning

confidence: 99%

“…Magnetization currents in the HTS tape conductor were found to be limiting [49,50,51]. In a similar effort, a layer wound Bi-2223 coil with brass laminated tape from Sumitomo was installed in a 500 MHz /14.1 T NMR system and approached solid-state NMR suitable field quality in a driven mode with a highly stabilized power supply and NMR feedback after allowing 2 weeks for the magnetization currents to recede [15].…”

Section: Brief History Of Insert Coilsmentioning

confidence: 99%

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High-temperature superconductors in high-field magnets

Weijers

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Preface and acknowledgementThis thesis deals with selected topics out of a wide research and development effort on HTS insert coil technology. Its origin goes back to the founding charter of the NHMFL in the year 1988 which listed the goal of realizing a 25 T superconducting magnet as one of the milestones the NHMFL was to achieve. High-temperature superconductors had only just been discovered and the required technology was non-existent. The path to where we are now has been eventful and a real learning experience. From the early days in the mid-1990-ies of the 'Wind and Pray" approach when coil testing relentlessly pointed out the shortcomings of both conductor and coil technologies at the time to the first successful "mini-coils" (around coil number 70) to the successive 1 T, 3 T and 5 T inserts (the latter reaching 25 T and bringing the total of numbered coils over 300 a decade later) to the promise of 30 + T superconducting user magnets with coated conductors in the not-toodistant future.Lacking the funds to buy the very expensive conductors, a collaboration was established with industry. This approach has served us well and resulted in a wide assortment of conductors to work with. New superconductors were donated in exchange for feedback on its performance as observed in our magnet technology development program. We also tested complete coils built by ourselves or by partners, in background magnetic field, a task for which the NHMFL facilities are well suited.This work is centered on the 5T insert coil for a total magnetic field of 25 T, but the research and development effort is interwoven with and inseparable from the broader HTS insert coil technology development program. Therefore discussions on a wider range of conductors and coils in line with the broader scope of this thesis are presented.While I take full responsibility for the described NHMFL insert coil designs, analysis and interpretation of the data on coils and conductors, having executed or been directly involved with all experiments described and having wound many a coil, this work has had the benefit of many direct and indirect contributions of a large number of people inside and outside the NHMFL. In contrast, developing this thesis itself has been the loneliest work I have ever done, but ultimately just as rewarding. There are many people that I would like to thank for their contributions to the HTS insert program in general and this thesis in particular.

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Section: Explicit Modelsupporting

confidence: 65%

Section: Brief History Of Insert Coilsmentioning

confidence: 99%

Section: Brief History Of Insert Coilsmentioning

confidence: 99%

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High-temperature superconductors in high-field magnets

Weijers

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“…High-temperature superconducting (HTS) coil is widely used in many applications because of its high critical current density in low temperature [1,2]. However, HTS coil has a disadvantage in aspect of thermal conductivity compared to low-temperature superconductors (LTS) [3].…”

Section: Introductionmentioning

confidence: 99%

Statistical analysis for HTS coil considering inhomogeneous I_cdistribution of HTS tape

Jin

Lee

et al. 2015

Progress in Superconductivity and Cryogenics

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Critical current of high-temperature superconducting (HTS) coil is influenced by its own self magnetic field. Direction and density distribution of the magnetic field around the coil are fixed after the shape of the coil is decided. If the entire part of the HTS tape has homogeneous I c distribution characteristic, quench would be initiated in fixed location on the coil. However, the actual HTS tape has inhomogeneous I c distribution along the length. If the I c distribution of the HTS tape is known, we can expect the spot within the HTS coil that has the highest probability to initiate the quench. In this paper, I c distribution within the HTS coil under self-field effect is simulated by MATLAB. In the simulation procedure, I c distribution of the entire part of the HTS tape is assume d to follow Gaussian-distribution by central limit theorem. The HTS coil model is divided into several segments, and the critical current of each segment is calculated based on the-generalized Kim model. Single pancake model is simulated and self-field of HTS coil is calculated by Biot-Savart's law. As a result of simulation, quench-initiating spot in the actual HTS coil can be predicted statistically. And that statistical analysis can help detect or protect the quench of the HTS coil.

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“…Further mechanical features as well as details of the LH700 have been previously reported. [3][4][5] For field mapping, a 0.7 µl sample 1 H NMR probe was traced along a helical path over a cylindrical surface of 17 mm diameter and 30 mm long in 12 revolutions. More than 256 points were acquired and statistically analyzed.…”

Section: Introductionmentioning

confidence: 99%

Development of a 700MHz low-/high- temperature superconductor nuclear magnetic resonance magnet: Test results and spatial homogeneity improvement

Hahn

Bascuñán

Lee

et al. 2008

Review of Scientific Instruments

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For the first time in nuclear magnetic resonance (NMR) magnet development, a magnet configuration comprising an insert wound with high-temperature superconductor (HTS) and a background-field magnet wound with low-temperature superconductor (LTS) has been proven viable for NMR magnets. This new LTS/HTS magnet configuration opens the way for development of 1 GHz and above NMR magnets. Specifically, a 700 MHz LTS/HTS NMR magnet (LH700), consisting of a 600 MHz LTS magnet (L600) and a 100 MHz HTS insert (H100), has been designed, built, and successfully tested, and its magnetic field characteristics were measured and analyzed. A field homogeneity of 172 ppm in a cylindrical mapping volume of 17 mm diameter by 30 mm long was measured at 692 MHz and corresponding 1 H NMR signal with 1.9 kHz half-width was captured. Two techniques, room-temperature and ferromagnetic shimming, were analytically examined to investigate if they would be effective for further improving spatial field homogeneity of the LH700. This paper reports on a world-first low-/high-temperature superconductor (LTS/HTS) 700 MHz nuclear magnetic resonance (NMR) magnet (LH700), designed, built, and successfully tested at the MIT Francis Bitter Magnet Laboratory (FBML). In the LH700, a 100 MHz HTS insert (H100) was placed in the cold bore of a 600 MHz LTS magnet (L600). Although a 950 MHz all-LTS NMR magnet is the latest achievement, 1 it is generally agreed among magnet engineers that 1 GHz is the practical frequency limit for all-LTS NMR magnets. We believe that the HTS capable of functioning at magnetic fields substantially greater than those of the LTS will play an increasingly prominent role in NMR magnets with operating frequency of 1 GHz and above.The key design philosophy adopted for the H100 includes (1) use of Bi2223-Ag composite tape and (2) a magnet configuration of stacked double-pancake (DP) coils-both for the first time in the history of NMR magnet development. Advantages of the DP coil-based HTS insert include (1) a conductor length typically required, <~200 m, for one DP coil is much less than that necessary, >5000 m, for its layer-wound counterpart, because it is much easier to obtain HTS tape meeting design specifications in short rather than long lengths; (2) DP-coil assembly permits placement of each DP coil, at an axial position within the insert assembly, according to the B ext versus I c characteristics of an individual DP coil that are most favorable to its currentcarrying capacity, thereby maximizing the overall critical current density; (3) axial space between adjacent DP coils may be varied for field profiling with spacers of different thicknesses between DP coils; and (4) in a DP-coil assembly, only defective DP coils need to be replaced rather than the entire insert, as it would be with a layer-wound insert.The H100 consisted of 48 DP coils, each wound with stainless steel reinforced Bi2223-Ag three-ply tape manufactured by American Superconductor Corp. (AMSC). Every DP coil in the H100 was wound in house, with a windi...

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An LTS/HTS NMR Magnet Operated in the Range 600–700 MHz

Cited by 29 publications

References 3 publications

High-temperature superconductors in high-field magnets

High-temperature superconductors in high-field magnets

Statistical analysis for HTS coil considering inhomogeneous I_cdistribution of HTS tape

Development of a 700MHz low-/high- temperature superconductor nuclear magnetic resonance magnet: Test results and spatial homogeneity improvement

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An LTS/HTS NMR Magnet Operated in the Range 600–700 MHz

Cited by 29 publications

References 3 publications

High-temperature superconductors in high-field magnets

High-temperature superconductors in high-field magnets

Statistical analysis for HTS coil considering inhomogeneous Icdistribution of HTS tape

Development of a 700MHz low-/high- temperature superconductor nuclear magnetic resonance magnet: Test results and spatial homogeneity improvement

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Product

Resources

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Statistical analysis for HTS coil considering inhomogeneous I_cdistribution of HTS tape