Superconducting Magnet Technology

Iwasa, Y.

doi:10.1007/b112047_1

Cited by 103 publications

(121 citation statements)

References 19 publications

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“…At the measured critical current value, voltage meets critical criterion V 0 like (7). By subtracting bypassed current through stabilizer layer as written in (8), we can calculate I c .…”

Section: Parameter Determination From Measurement Datamentioning

confidence: 99%

A study on a modeling method about current-voltage characteristic of HTS tape considering resistance of stabilizer

Lee

Nam

et al. 2013

Progress in Superconductivity and Cryogenics

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Current-voltage characteristic models of superconducting material are suggested by many researchers. These current-voltage characteristic models are important because they can be used for design or simulation of superconductor devices. But widely used current-voltage models of superconductor wire still have some limitations. For example, a standard E-J power model has no parameters related with stabilizer's resistance in superconductor wire. In this paper, a current-voltage characteristic modeling method for high temperature superconductor (HTS) tape with considering the effect of stabilizer is introduced. And a current-voltage characteristic of a HTS tape is measured under different stabilizer conditions. Those measured current-voltage characteristics of the HTS tape modeled with proposed modeling method and the modeling results are compared.

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“…At the measured critical current value, voltage meets critical criterion V 0 like (7). By subtracting bypassed current through stabilizer layer as written in (8), we can calculate I c .…”

Section: Parameter Determination From Measurement Datamentioning

confidence: 99%

A study on a modeling method about current-voltage characteristic of HTS tape considering resistance of stabilizer

Lee

Nam

et al. 2013

Progress in Superconductivity and Cryogenics

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“…The Although the 100 T, in a bath of 4.2-K liquid helium, will be operated at 2400 A, shared among four parallel tapes, the winding itself is adiabatic, i.e., no liquid helium and thus no its vapor bubbles within the winding. 27 Due to the domineering overbands, the 100 T has an overall current density, ½kJ Magnet , of 30.9 A/mm 2 . Figure 3 shows plots of field and current parameters vs.…”

Section: -mentioning

confidence: 99%

“…26 A force balance equation, 27 Eq. (1), is applied to stress analysis, where r r and r h are radial and hoop stresses, while kJ and B z (r) are overall current density and field distributions within the winding, respectively.…”

Section: -25mentioning

confidence: 99%

First-cut design of an all-superconducting 100-T direct current magnet

Iwasa

Hahn

2013

Applied Physics Letters

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A 100-T magnetic field has heretofore been available only in pulse mode. This first-cut design demonstrates that a 100-T DC magnet (100 T) is possible. We base our design on: Gadoliniumbased coated superconductor; a nested-coil formation, each a stack of double-pancake coils with the no-insulation technique; a band of high-strength steel over each coil; and a 12-T radial-field limit. The 100 T, a 20 mm cold bore, 6-m diameter, 17-m height, with a total of 12 500-km long superconductor, stores an energy of 122 GJ at its 4.2-K operating current of 2400 A. It requires a 4.2-K cooling power of 300 W. A 100-T DC field, one million times the earth field, is more than double 45 T, 1 the highest DC field created to date. Upon completion, a 32-T magnet at the National High Magnetic Field Laboratory (NHMFL) will achieve the highest DC field by an all-superconducting magnet.2,3 Fields greater than 45 T have been beyond DC magnet technology. Simply stated, this is because no electrical conductor meets two requirements for generation of a >45-T continuous field: high mechanical strength and good electrical conductivity. Copper is unable to withstand the high magnetic stresses. Steel can cope with the large stresses, as has been demonstrated by pulse magnets, 4,5 but its large electrical resistivity leads to huge Joule heating that rapidly overheats the steel, reducing its strength and thereby forcing >45-T steel magnets to operate only in pulse mode. 6,7 Although the range of experiments that can be done with pulsed fields continues to expand, 7 the words of Francis Bitter remain valid, "there are many experiments that are extremely difficult or impossible to perform in a hundredth of a second" 8 as a reason to drive the maximum DC field limit much higher. Our 100-T DC magnet (100 T) uses a superconductor of sufficient strength, with the winding reinforced by overbands of high-strength stainless steel. With electrical resistivity anchored to zero, one inherent weakness of the pulse magnet is eliminated.The two crucial design issues in high-field superconducting magnets are: (1) mechanical integrity; and (2) protection. In this first-cut design, based on the no-insulation (NI) technique, 9-18 we assumed 100 T self-protecting; thus, we focused chiefly on mechanical stress. Our key design approach is fourfold. The 100 T is wound with GdBCO tape manufactured bySuperPower, specifically 12-mm wide and 95-lm thick, comprising 50-l thick Hastelloy substrate (room-temperature yield stress and strain, respectively, of 970 MPa and 0.95% 19 ), two 20-lm thick electroplated copper layers, and 5-lm thick remainder (1-lm thick GdBCO layer and other materials). 2. The 100 T consists of 39 nested coils, each a stack of double-pancake coils (DPs) wound with the NI technique.3. To keep the peak tensile stress on GdBCO tape to 700 MPa at 4.2 K, each DP is reinforced over its outer diameter with a high-strength stainless steel band (overband) of 300-K ultimate strength of 1400 MPa and Young's modulus of 200 GPa. 4. To limit the maximum radial fi...

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“…1,[4][5][6][7][8][9][10] We may thus consider a superconducting coil as a Bean cylinder of a diamagnetic wall D thick. 4 Although D cannot be equated directly to the size of a superconductor strand, typically $50 lm for LTS and millimeters for HTS, LTS coils generally have much less attenuating and distorting effects of the diamagnetic wall than HTS coils. However, a sheer size of LTS in a typical all-LTS NMR magnet makes diamagnetic effects in LTS magnets not negligible.…”

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confidence: 99%

“…Note that for a Z1 shim comprising two rings, a gap distance of ffiffi ffi 3 p a results in a Z1 field free of the Z3 (d 3 Bz=dz 3 ) term. 4 For 2a ! 48:5 mm, e.g., 74 mm ( ffiffi ffi 3 p a ' 64 mm), two 36-mm wide (32 mm þ 4 mm) tapes may be overlapped axially as illustrated in Fig.…”

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confidence: 99%

Persistent-mode high-temperature superconductor shim coils: A design concept and experimental results of a prototype Z1 high-temperature superconductor shim

Iwasa

Hahn

Voccio

et al. 2013

Applied Physics Letters

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Design, fabrication, and test results of a type persistent-mode high-temperature superconductor (HTS) shim coil are presented. A prototype Z1 rectangle-loop shim, cut from 46-mm wide Y-Ba-Cu-O tape manufactured by AMSC, was fabricated and tested at 77 K. The HTS shim, much thinner than the conventional NbTi shim, is placed inside the main magnet and immune to its diamagnetic wall effects. Combined with the >12-T and >10-K operation capability, the HTS shim offers a versatile design option for nuclear magnetic resonance (NMR) magnets, liquid-helium-free as well as conventional, and is particularly attractive in the next generation NMR magnets. For the NMR (nuclear magnetic resonance) superconducting magnet, its field over a target space where a specimen (the object of spectroscopy) is placed must be very homogeneous. For a high-resolution NMR magnet, this inhomogeneity can be as severe as 0.01 ppm over a 30-mm diameter spherical volume (DSV). The "raw" field of most superconducting magnets is not good enough for NMR spectroscopy and therefore it must be shimmed to a homogeneous field over the specimen volume. [1][2][3] Generally, the superconducting NMR magnet is equipped with its own set of superconducting shim coils ("shims"), currently all wound with NbTi, a low-temperature superconductor (LTS). Because of their field limitations (<12 T even at 1.8 K) and size (typically 15-30 mm radial build), NbTi shims have always been located outside the magnet assembly, i.e., radially furthest away from the magnet center where the sample is placed. This is chiefly because no superconducting shims suitable for the high-field center region have been available. Here, we describe the design concept of the high-temperature superconductor (HTS) shims and results of a prototype Z1 shim, built and operated.For a shim placed outside the magnet assembly, there are two inherent technical disadvantages: (1) at a great distance it must work harder to generate a required shimming field, i.e., a greater ampere (current)-turns (coil size); and (2) its field is attenuated by the "diamagnetic" walls of the magnet assembly, comprising many superconducting coils, as it reaches the magnet center. Worse, this field attenuation is asymmetric to the center and has strong hysteresis.Diamagnetic effect is the manifestation of a screening current induced by a field impinging on a "Bean" cylinder. 1,4-10 We may thus consider a superconducting coil as a Bean cylinder of a diamagnetic wall D thick. 4 Although D cannot be equated directly to the size of a superconductor strand, typically $50 lm for LTS and millimeters for HTS, LTS coils generally have much less attenuating and distorting effects of the diamagnetic wall than HTS coils. However, a sheer size of LTS in a typical all-LTS NMR magnet makes diamagnetic effects in LTS magnets not negligible.In this paper, we describe a design concept for superconducting shims prepared from a "wide" tape of coated YBCO HTS. 11,12 The HTS shim can operate even in a >12-T field and above liquid helium (LHe) tempe...

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Superconducting Magnet Technology

Cited by 103 publications

References 19 publications

A study on a modeling method about current-voltage characteristic of HTS tape considering resistance of stabilizer

A study on a modeling method about current-voltage characteristic of HTS tape considering resistance of stabilizer

First-cut design of an all-superconducting 100-T direct current magnet

Persistent-mode high-temperature superconductor shim coils: A design concept and experimental results of a prototype Z1 high-temperature superconductor shim

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