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The Tsukuba Magnet Laboratory and the High Field Laboratory for Superconducting Materials collaborated on developing the next-generation 50 T-class hybrid magnet. One of the properties to be incorporated into this next-generation hybrid magnet is energy-saving operation in generating a high-strength magnetic field. This report presents the estimated performance of this hybrid magnet, on the basis of a 20 T \varnothing440 mm room temperature bore for the superconducting outsert magnet, DC power of 15–24 MW for a three-layered Bitter resistive insert magnet, and a \varnothing32 mm room-temperature bore for the resistive insert magnet. Cu–Zr (Cu–Ag) alloy is assumed material to be used for the outermost layer (inner two layers) of the Bitter magnet. The estimation indicates that the hybrid magnet generates magnetic fields beyond 47.9 T (49.1 T) for a resistive insert magnet operation power of 15 MW (24 MW) in a 20 T background magnetic field, where the upper-limit design stress on the innermost Bitter coils is tentatively assumed to be 800 MPa. An ultimate tensile strength exceeding 1140 MPa with a conductivity of 72% International Annealed Copper Standard (IACS) for a Cu–Ag alloy plate would be necessary to meet the design stress of 800 MPa. Using this material, we could make the 15 MW water-cooled resistive insert magnet (WM) for this energy-saving, compact hybrid magnet that generates magnetic fields of 47 T and beyond. For a moderated upper-limit design stress of 760 MPa, the corresponding magnetic fields of the hybrid magnet are 47.5 and 48.5 T. [ABSTRACT FROM PUBLISHER]

A nuclear magnetic resonance (NMR) system using a high-temperature superconducting (HTS) magnet and a probe with an HTS radio frequency coil is currently under development. The HTS NMR magnet is expected to reduce the volume occupied by the magnet and to encourage users to install higher field NMR systems. RE-Ba-Cu-O-coated (REBCO-coated) conductors offer the advantages of a higher critical current density than low-temperature superconductors in magnetic fields above 10 T as well as tolerance to high tensile stress. Both of these factors are expected to lead to a reduction in the volume of the magnet. Four REBCO layer-wound test coils were fabricated in order to investigate their properties under electromagnetic forces in an external magnetic field of up to 17. 2 T. The REBCO coils with a practical inner diameter were successfully operated under electromagnetic forces of over 200 MPa in high magnetic fields. [ABSTRACT FROM PUBLISHER]

This paper presents magnetic-field distributions generated by screening currents flowing in short and straight multiple coated conductors exposed to a high magnetic field. The purpose of this study is to understand interactions between the magnetic field and the screening currents flowing in the coated conductors. In this paper, we suggest a method for calculating the magnetic-field distributions from current distributions. The method takes into account of the mutual screening current in the coated conductors. The magnetic-field distributions estimated using the method are in agreement with the experimental results. In addition, the current distributions inducing the magnetic-field distributions are described. [ABSTRACT FROM PUBLISHER]

Using high-Tc superconductors (HTS) is considered to be the only solution to dramatically increase the highest fields of NMRmagnets because of their high critical fields. However, it is not easy to apply HTS to an NMR spectrometer (HTS-NMR) because a persistent-mode operation with HTS cannot satisfy the field stability of 0.01 ppm/h at present. To overcome this problem, we are now developing an HTS-NMR spectrometer in a driven-mode operation. As the first step, a layer-wound coil was fabricated with bronze-reinforced Bi-2223 conductors. Instead of the Nb3Sn coil, the Bi-2223 coil was installed as the innermost part of an existing NMR magnet. The magnet operated at a field of 11.7 T with a highly stabilized power supply. NMR measurements were carried out, and it was demonstrated that the quality of the multi-dimensional NMR spectra on the protein was equivalent to that obtained with a persistent-mode system. The next step will be to demonstrate its usefulness as a high-field NMR system. The upgrade of the 920 MHz NMR system installed at the Tsukuba Magnet Laboratory is underway. Its innermost coil is scheduled to be replaced by a Bi-2223 layer-wound coil for 2010. Its target field is 24.2 T (1.03 GHz). [ABSTRACT FROM AUTHOR]

A numerical simulation method which deals with the screening current-induced magnetic field for YBCO coils, including the self field effect induced by the transport current, has been developed. The simulation agrees well with the experimental results for an YBCO solenoid. Based on the numerical simulation, the effect of coil shape on the screening current-induced magnetic field intensity for the YBCO coils has been investigated. The field was demonstrated to reach a maximum if the solenoid corresponds to the minimum-volume design; it amounts to as large as -18% of the central magnetic field. Two major problems must be considered for YBCO coils regarding the screening current: (a) a reduction in the central magnetic field by the screening current and (b) a temporal drift of the apparent magnetic field due to relaxation of the screening current by flux creep. It is suggested that the latter can be suppressed by a current sweep reversal technique. [ABSTRACT FROM AUTHOR]

In this study, we investigated in field properties of high-Tc superconductor (HTS) tapes electrically as well as mechanically. Metallic reinforced Bi-2223/Ag superconductor tapes were used in this work. The critical current (Ia), which is highly dependent on the magnetic field, was measured using fields applied parallel and perpendicular to the tape surface. The conductor was exposed to fields of up to 28 T at 4.2 K. In order to confirm the performance of tapes in practical NMR operation, Ic was also measured around 2 K. The conductor was wound on a large diameter bobbin and mechanical properties were then measured as the coil current was increased. Finally, we verified the conductor properties from coil Ic and maximum stress/strain of it. [ABSTRACT FROM AUTHOR]

The electromagnetic stress distribution inside a HTS insert is one of the key issues for construction of a high field high/low temperature superconductor (HTS/LTS) magnet. The r · J · B formulae is widely used for the stress calculation of the coil, due to its simplicity. However, the assumption of this calculation makes it impossible to consider the effects of the bobbin, an epoxy impregnated structure, on stress of the coil. In this work, stress analysis methods are reported. The governing equation defined from the force equilibrium state was adopted and used to analyze what the stress of the HTS coil wound with Bi2223/Ag conductor. The validness of the stress analysis method was confirmed by comparison with experimental results, especially in the coil with epoxy impregnation. The numerical and experimental procedures are described and both results are discussed. [ABSTRACT FROM AUTHOR]

Electrical and mechanical characteristics of Type HT tape, which is standard 4.2 mm wide DI-BSCCO tape reinforced with metallic tapes, have been evaluated. Longitudinal distributions of critical current and n-index in kilometer long Type HT tape has proved uniform from end to end just like the original insert tape, which is Type H tape. Type HT-CA reinforced with 50 μm thick heat-resistant copper alloy is highly balanced tape with high mechanical properties and low splice resistance. Type HT-SS reinforced with 20 μm thick stainless steel has the best mechanical properties, which has been demonstrated under the actual environment in high field magnet, namely the hoop stress load test energizing a one-turn coil in external high magnetic field and liquid helium. [ABSTRACT FROM AUTHOR]

Coated conductor tapes are promising materials for the construction of high field inserts (>20 T). In a magnet, the magnetic field at the coil ends is not parallel to the wide face of the tape, and the angle can reach values larger than 10 degrees. Coated conductors have very anisotropic transport properties, thus it is very important to measure the angular dependence of the critical current. The critical current of commercial YBCO coated conductors made by Super-Power has been measured at 12 T, 4.2 K as a function of the angle between the magnetic field and the wide face of the tape, with a precision of less than 0.2 degree. The experimental results have been used for designing insert coils for high field magnets: depending on the coil parameters and current, the high sensitivity to the magnetic field angle of YBCO tape can affect the performances of the coil. [ABSTRACT FROM AUTHOR]

Mg addition improves Tc, Birr, and Ic of the Nb3 Sn formed by diffusion reaction between Nb and Ag-Sn alloy, when the diffusion reaction is performed below 650°C. The obtained superconducting properties are similar to those of the bronze-processed Nb3Sn. The formation temperature of Nb3 Sn is reduced by the Mg addition. By using OM, SEM, and field emission type EPMA, we could not measure the thickness of Nb3Sn Iayers, which may be thinner than 0.5 μm. It is not clear that the Mg addition increases the formation rate of Nb3Sn. However, the Nb3Sn layers should have very high Jc. The attainable overall Jc of the Nb3Sn wire are as high as those of the bronze-processed Nb3Sn wire without Ti and Ta additions, although the optimization of the cross-sectional configuration of Nb and Ag-Sn-Mg in the wire has not yet performed. Therefore the potential of the Nb3Sn conductor made by the new process seems to be very attractive for the practical applications. [ABSTRACT FROM AUTHOR]

A program to develop a 30 T superconducting magnet based on novel concepts is now in progress at the High Field Laboratory for Superconducting Materials (HFLSM) at Tohoku University and the Tsukuba Magnet Laboratory (TML) at the National Institute for Materials Science. A 30 T superconducting magnet comprising a high-temperature superconducting (HTS) insert and a low-temperature superconducting (LTS) outsert was conceptually designed. For the high-field HTS insert, a YBCO coated conductor tape was adopted because of its high critical current density in high fields and its high mechanical strength. A relatively high tolerance limit of hoop stress in the insert coil can be assumed in the coil design according to its mechanical properties. The critical current density of the YBCO tape was analytically predicted as a function of temperature and magnetic field. To withstand a large electromagnetic force, the LTS outsert was composed of CuNb/Nb3Sn and NbTi coils. The CuNb/Nb3Sn coil was designed using high-strength cable consisting of internally reinforced Nb3 Sn strands with a CuNb reinforcing stabilizer subjected to repeated bending treatment. The results of this design study show the potential for a compact high-field magnet employing an insert coil formed of YBCO coated conductor. [ABSTRACT FROM AUTHOR]

A magnet that allows horizontal as well as vertical access to the magnet center is suitable for industrial applications. We designed and fabricated a split-paired magnet cooled with two G-M refrigerators. The magnet has a vertical room-temperature bore of 400 mm in diameter and a horizontal room-temperature gap of 73 mm. Its design value of field uniformity around the magnet center is 0.53% in a space 200 mm in diameter and 50 mm in height. The magnet successfully operated up to 3 T. It was applied to produce anisotropic conductive sheets. Anisotropic conductive materials that are composed of dispersed contacts in polymer film are indispensable for electrical connections in multimedia devices. The magnet was combined with a sheet-forming machine that could press a mold up to 5 tons and 473 K. By using the mold with finely arranged ferromagnetic pins, the production of anisotropic conductive sheets with highly dense contacts and high reliability was successfully achieved. [ABSTRACT FROM AUTHOR]

A new 52-mm warm-bore resistive insert for a hybrid magnet was designed and constructed at the Tsukuba Magnet Laboratory (TML) of the National Institute for Materials Science (NIMS). This magnet successfully generated a peak magnetic flux density of 35.5 T at the operating current of 34.88 kA and 367.5 V with a background field of 14.05 T. To supply the high magnetic fields for more time in the 52-mm warm bore, an axially cooled three-coaxial-coil structure and a staggered layout of the elongated cooling holes were adopted for Bitter disks after a parameter survey that was conducted to consider a reduction in the operating electric power. Disks were stacked in a modified Weggel scheme on a turntable with a rotating angle controlled by the stacking data of each coil. The innermost coil was connected electrically in series with the two outer coils connected in parallel. The Bitter disks used in the coils were made from two kinds of Cu-Ag plates. The magnet is now in operation for users. [ABSTRACT FROM AUTHOR]

The water-cooled insert magnet of the TML hybrid magnet successfully generated 37.9 T in a 32-mm room- temperature bore with a 14.02 T buckup field generated by a superconducting outsert magnet. At that magnetic field, the maximum electric power for the insert magnet was 13.35 MW. This Bitter-type insert magnet is divided into three coaxial coils, and the innermost coil consists of two coaxial coils. The inner coil is connected in series with the outer two coils connected in parallel. The Bitter plates for the outermost coil were made of GlidCop AL-25, and those for the other coils were made of hard-worked Cu-Ag plates. The thickness of the Cu-Ag plates was 0.40 mm, and the average 0.2 % yield strength was about 810 MPa at 373 K. [ABSTRACT FROM AUTHOR]

The performance of a flux concentrator using an YBCO oxide superconductor was tested to raise the steady state magnetic field generated by the existing magnet. This concentrator was composed of an outside hollow cylinder and a pair of half cylinders that goes in and out in the outside cylinder. This flux concentrator generated additional magnetic field more than 1.6 T for an applied magnetic field 28 T. [ABSTRACT FROM AUTHOR]

We fabricated 55-filament Bi-2223/Ag tape and evaluated the dependence of critical current (Ic) and index n in an external magnetic field up to 30 T at 4.2 K, in order to explore the possible application for a magnet in persistent current mode. Ic and index n were characterized as a function of temperature and the magnitude and orientation of the magnetic field by increasing and decreasing field. It was observed that Ic was dependent on the magnitude and orientation of the magnetic field. The Ic decreased exponentially as the field increased; in a parallel and increasing field, Ic was 128 A at 30 T, which is approximately 40 % of the Ic in self-field. On the other hand, index n was not significantly dependent on the field up to 30 T, nor did it vary significantly on increasing or decreasing field; the n value in the range of 0.1 ∼ 1 μV /cm was 23.0±5.2 and 27.8±8.0 on increasing and decreasing field, respeclively, in the range of 0∼30 T. In addition, we observed that local Ic and index n of a long length of tape (4.2 m) were dispersed over a wide range and that the variation of each of these two values with the position of the tape was similar, suggesting that these properties depend on the microstructural uniformity. [ABSTRACT FROM AUTHOR]

A new MHD (magnetohydrodynamics) generator based on electromotive force using seawater, that is, a helical-type seawater MHD generator with a 7 T solenoid superconducting magnet, is designed, constructed and tested. The constructed generator contains a helical insulation wall made of polyvinyl chloride 140 mm long and 100 mm in diameter, an anode rod made of SUS316 1350 mm long and 10 mm in diameter, and a cathode pipe made of SUS316 260 mm long and 100 mm in diameter. In the experiment, electromotive force and generator output are measured in terms of average flow velocity (0-5.6 m/s) and magnetic field (0-7 T) using artificial seawater (3.4% NaCl aqueous solution). As a result of the experiment, it was found that the electromotive force increases proportionally to average flow velocity and magnetic field, and that the generator output increases quadratically to average flow velocity and magnetic field over certain points. Experimental values are discussed by comparing the theoretical values and computed values. [ABSTRACT FROM AUTHOR]

Examines the persistent-mode operation of a high temperature superconducting magnet cooled by a cryocooler. Thermal conductance; Decay behaviors; Temperature increase of the magnet due to persistent current switch.

Describes the superconducting NMR magnet developed at the Tsukuba Magnet Laboratory in Japan in 1999. Manufacture of the magnet with 15-percent tin-bronze-processed (Nb,Ti)[sub 3]Sn, Tantalum-reinforced (Nb,Ti)[sub 3]Sn and NbTi conductors; Cooling of coils used with pressurized superfluid helium.

We set out to design as compactly as possible a 30 T superconducting magnet consisting of an YBa2Cu3O7 (Y123) insert coil and a CuNb-reinforced Nb3Sn (CuNb/Nb3Sn) background coil. The engineering current density Je for an Y123-coated conductor tape is larger at 14–15 T and 4.2 K than that for a CuNb/Nb3Sn strand. Adopting Y123-coated conductor tapes in the high field region above 14–15 T proves highly effective for the fabrication of a very compact 30 T superconducting magnet. A 30 T, 52 mm-room-temperature bore superconducting magnet can be constructed in the coil grading of a 16 T Y123 insert and a 14 T CuNb/Nb3Sn background coil, and the stored magnetic energy of 32 MJ successfully lies in the 1/3 level in comparison with the 30 T nuclear-magnetic-resonance (NMR) superconducting magnet reported previously. [ABSTRACT FROM AUTHOR]

High-temperature superconductors (HTS) are considered to be indispensable to realize NMR magnets that exceed 1 GHz owing to their high critical current densities even in high magnetic fields exceeding 20 T. Feasibility studies of the > 1-GHz NMR magnet with the HTS inner coil have been reported. HTS conductors are brittle, and it is not easy to apply to superconducting coils such as the inner coils of the > 1-GHz NMR magnet. Investigations into the mechanical properties of HTS coils are quite important. The hoop stress is an important factor in magnet design. Bi-2223 conductors are most promising because they are commercially available and can be obtained with lengths of more than 1,000 m. Double pancake coils with an inner diameter of 260 mm wound from Bi-2223/Ag conductors of the Sumitomo DI-BSCCO (high-Ic type and high-strength type) were fabricated to evaluate the hoop stress dependence of the critical current of the coil. The double pancake coils were tested using the 14-T superconducting magnet with a room temperature bore of 400 mm in diameter at the Tsukuba Magnet Laboratory (TML). The critical current of the high-Ic test coil was 164 A, where the hoop stress was estimated at 323 MPa. The critical current decreased to 140 A after energizing the coil above a hoop stress of 300 MPa. The high-strength test coil burst at a hoop stress of approximately 200 MPa. [ABSTRACT FROM AUTHOR]

We have proposed new applications of bulk high-temperature superconductors in high magnetic fields. High-temperature superconductors, such as BSCCO or YBCO, maintain their superconductivity over 30 T at 4.2 K. A field-cooled superconducting hollow cylinder traps the magnetic flux inside itself. A field-cooled superconducting solid cylinder traps in the interior of it. An increase of the applied magnetic field induces shielding current in the interior of the cylinder to maintain the magnetic flux constant. By suitably arranging the cylinders, we can concentrate the magnetic flux and enhance the gradient of the magnetic field. In order to confirm these concepts, we performed experiments using bulk YBCO cylinders. The cylinders are made of Yba2Cu3O7-x quasisingle crystals containing Y2BaCuO5 particles. Hollow and solid cylinders were employed to concentrate the magnetic flux. Using three hollow cylinders, the concentrated magnetic field of 0.49 T was observed in the applied magnetic field of 10.14 T. The concentrated magnetic field of 0.64 T was observed for the solid cylinders in the applied magnetic field of 10.24 T. The magnetic flux concentration was observed even in the high magnetic field over 20 T. [ABSTRACT FROM AUTHOR]

Magnetic field direction often greatly influences material properties, such as critical current densities of tape-shaped superconductors. To determine the influence of this parameter, an object is usually rotated in a fixed magnetic field, which is not always effective. We are developing a variable-fieId-direction superconducting magnet that can change its field direction continuously in a two-dimensional plane. Two sets of split-pair coils are placed perpendicular to each other, and the perpendicular magnetic fields generated by each split-pair coil are superimposed. By independently controlling the operating current of each split-pair coil, we can continuously change the direction of the superimposed magnetic field. Four solenoid coils were wound with Nb-Ti conductors. This magnet is designed to rotate a field of 1 T. The field homogeneity is estimated to be less than 1 % in a 10 mm-diameter sphere volume. This is a conduction-cooled superconducting magnet employing 4K-GM refrigerators. We constructed a cryostat with two types of room-temperature bores and conducted a cooling test without solenoid coils and supporting structures was conducted. [ABSTRACT FROM AUTHOR]

Examines the design and fabrication of superconducting magnet used for generating uniform and high magnetic force fields. Niobium alloy composition of the conductor; Central magnetic field of the magnet; Cooling of the magnet using cryocoolers.

The magnetization loss of MgB wire was investigated using numerical calculations based on the finite element method. Various superconducting properties of MgB wire such as nonlinearity and the field dependence of the critical current were considered in the numerical formulation. An analysis of magnetization loss was carried out as a function of the external magnetic field for a wide range of operating temperatures. The numerical results were compared with conventional theories and were found to be in relatively good agreement. An alternate approach based on a normalization method using critical current data was also employed as a simple method for predicting magnetization loss. The effectiveness of the simple equation for predicting loss was verified by comparisons of both values for various temperatures. [ABSTRACT FROM AUTHOR]

Abstract: The direct production of Nb3Al superconducting coils using the combinational technology of ‘cold spray’ as physical deposition and ‘electron beam’ as surface modification has been proposed. Using this method, the helical line of the Nb3Al superconductor is produced directly on a cylinder without conventional wiring process. In order to prove the possibility of direct coil production, we first made flat-plate and cylindrical samples, and then examined the characteristics as superconductor. The flat-plate samples showed the phase transition in magnetization and the characteristics of superconductivity when the output powers of the electron beam were over 800W at a beam speed of 3m/s and 1200W for 6m/s. It was confirmed that a 10-turn single-layer coil with a ϕ40mm diameter and a length of 50mm generated a magnetic field of 2.7mT at 20.5A. [ABSTRACT FROM AUTHOR]

Abstract: We have commenced a project to develop a beyond-1GHz solution NMR spectrometer using a HTS coil. Due to a small residual resistance present in the HTS conductor and joint resistance between conductors, a stable persistent current sufficient for NMR measurements is unlikely. Therefore, a current has to be supplied to the HTS coil from an external power supply. The ripple of an external power supply causes a field fluctuation which must be stabilized. In this study we show results of NMR measurements using a 500–600MHz NMR in such an external current mode: the field fluctuations are stabilized by an internal 2H lock. The field fluctuation from the external power supply comprises a major field fluctuation component at low frequencies, 0.003–0.005Hz, and superimposed minor field ripples at 2Hz and 50Hz. The former limits the time interval of the internal 2H lock, while the latter generates sidebands in the NMR spectrum. Sideband and baseline noise are controlled by appropriate selection of the feedback loop parameters of the lock. The quality of the 1D-solution NMR spectra observed in external current mode is equivalent to that obtained in persistent current mode. However, if the feedback loop time is as short as the gradient pulse width, refocusing of the NMR signal is lost and NMR peaks disappear. The 2D-NOESY and the 2D-HSQC spectra of ubiquitin in an external current mode have been acquired. The quality of the 2D spectra is equivalent to those obtained in persistent current mode; i.e. the internal 2H lock operates stably over an experimental time interval of 40–50min. To realize a beyond-1GHz NMR spectrometer, further investigations must be made of (i) the long term stability of a DC power supply, (ii) the enhancement of the compensation field limit for the internal 2H lock, (iii) the extension of the helium refill time interval, and (iv) a method to correct the field homogeneity in the external current mode. [Copyright &y& Elsevier]

We investigated the superconducting properties of Nb3Sn formed through the diffusion reaction between Nb and Ag-Sn alloys, including Ag-9at%Sn ductile fcc phase and Ag-(12–16)at%Sn ductile ζ phase alloys, and Ag-24at%Sn brittle e phase alloy. We fabricated single-core and multi-core composite wires by the rod-in tube and powder-in-tube processes. The composite wires were heat treated at 650–900°C to form Nb3Sn filaments. With increase of Sn content in the Ag-Sn alloy cores, the superconducting properties of the Nb3Sn composite wires were improved. Tc and Bc2 (4.2 K) values for the Nb/Ag-Sn wires are similar to those for the Nb/Cu-Sn. However the Ic values are relatively small, due to their very thin Nb3Sn layers below 0.4 μm. Ag is apparently not effective to increase the formation rate of Nb3Sn layer. By using the 200- and 40000-core wires, Tc and Bc2 (4.2 K) values were increased by 0.5–1 K and 2–5 T, respectively for these multifilamentary wires, while from 10 to 500 times larger Ic, (4.2 K) were obtained for the wires. The typical values for Tc and Bc2 (4.2 K) are 16.5–17.7 K and 16–21 T, respectively. The addition of 5at%Cu to Ag-Sn alloys improves their superconducting properties. [ABSTRACT FROM AUTHOR]

Abstract: 1H NMR spectra of G1-α-CD and G1-β-CD were recorded using a spectrometer equipped with a 21.6T magnet. An ultra-high magnetic field was effective for detecting 1H NMR signals with a small difference in chemical shifts. Introducing a glucosyl group onto CDs as a branch caused deformation of equilibrated 1H signals of cyclodextrin. Particularly, 1H signals in branched glucose were shifted greatly. [Copyright &y& Elsevier]