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Accurate simulation of the hysteresis loop is challeng-ing, especially using manufacturer data. Traditional parameter extraction methods (e.g., using optimization algorithm and solving transcendental equation) can extract the static Jiles-Atherton (JA) hysteresis model parameters under an arbitrary condition, but it requires fitting parameters because the model parameters vary with flux density. To reduce the dependence on measurement data, this paper proposes a simple but effective parameter extraction method. Firstly, an identification procedure of minor loop is presented using only static B-P loss curves by investigating the influence of model parameters on hysteresis loop, where the average root-mean-square error of the hysteresis loop is decreased by 4. To estimate the dynamic loss coefficients under DC bias, a calculation method based on the Statistical Theory of Losses (STL) is established by investigating the law of influence of DC bias on hysteresis loss and dynamic loss. The effectiveness of the proposed method is verified. [ABSTRACT FROM AUTHOR]

The Advanced Light Source (ALS) is a thirdgeneration light source in operation since 1993. This light source is providing state-of-the-art performance to more than 40 beamlines and their users, due to the upgrades that have been completed over the last few years. The storage ring upgrade project that is developed here will allow the ALS to provide the 40 beamline users with higher photon beam brightness (factor of 2 or 3) by having its storage ring lattice modified. Forty-eight harmonic sextupole magnets with integrated dipole correctors and skew quadrupole coils will be introduced, which will require a level of installation activity not seen at the ALS since its original construction in 1991. Introducing new combined-function magnets in an existing storage ring is a challenge due to the limited space available and a balance had to be found between magnet performance and spatial constraints. After an introduction reviewing the characteristics of the three design families of the 48 combined-function magnets, the magnet fabrication and installation are developed along with analyses based on the magnetic measurements and the ALS storage ring commissioning results.

Divertor Tokamak Test facility (DTT) is going to be built in Italy, and is expected to be operated along with ITER to explore the potential solution for the power exhaust to be eventually implemented in DEMO. 77 tons of Nb3Sn strand in two types are required by DTT. For type one, the weight is 55 tons. The dominant performance requirements are Ic >285 A (4.2 K, 12 T) and hysteresis loss <1000 mJ/cm3 (4.2 K, ± 3 T). For type two, the weight is 22 tons. The dominant performance requirements are Ic >260 A (4.2 K, 12 T) and hysteresis loss <400 mJ/cm3 (4.2 K, ± 3 T). These performance requirements are quite challenging in the respect of performance stability in Nb3Sn strand production. WST has successfully developed three types of Nb3Sn strand to meet these requirements especially for DTT. For DTT type one, considering the ultra-high level of Ic, Nb and Sn volume was increased based on the structure of WST Nb3Sn strand for ITER. Ic >300 A (4.2 K, 12 T) and hysteresis loss <700 mJ/cm3 (4.2 K, ± 3 T) have been obtained from both 164-filament structure and larger-filament structure. For DTT type two, Cu split structure was selected to guarantee low hysteresis level. For the structure with 160 filaments and one Cu split, Ic >260 A (4.2 K, 12 T) and hysteresis loss <400 mJ/cm3 (4.2 K, ± 3 T) have been achieved. Finally, all the performance of DTT Nb3Sn strand has been accomplished by WST. [ABSTRACT FROM AUTHOR]

Experimental and advanced superconducting Tokamak (EAST) was designed by the Institute of Plasma Physics Chinese Academy of Sciences. The magnet system of EAST includes poloidal field (PF) coils, central solenoid (CS) coils, and toroidal field coils. The heat generated by the ac losses of PF and CS coils increases the burden of the cooling system, which reduces the critical current of the superconducting cable. Once the superconducting magnet quenches, it will pose a serious threat to the stability of the whole device. In this paper, the piecewise linear method and the finite-element analysis were used to analyze the ac loss of the EAST PF and CS coils under the specific operating current. The whole calculation process is described in detail. The final results meet the stability margin of the design of the EAST device. Meanwhile, the ac losses of PF and CS coils for EAST are theoretically evaluated in terms of the structure of magnet, the simplified current, and the distribution of the coil. The results of this paper not only provide data support for the next design and experiment of the EAST device, but provide some references for similar calculation of other large nuclear fusion magnets. [ABSTRACT FROM AUTHOR]

This thesis presents a new type topology structure of superconducting solid fault current limiter (SSFCL). A group of academic researches on the new type topology structure of SSFCL are briefly performed. First, this paper reasonably analyses the hysteresis control mode of SSFCL and determines the superiority of its application. Then, the mathematical simulation model of SSFCL is built and the reliability of SSFCL is verified by simulation. By comparing the simulation results of SSFCL, solid fault current limiter, and superconducting fault current limiter, the conclusion can be drawn that the SSFCL is more stable and more effective on controlling the increase rising rate of a short-circuit current. [ABSTRACT FROM AUTHOR]

High temperature superconducting (HTS) maglev train running in the evacuated tube is a new kind of transportation with great potential. The HTS bulks are core component of the HTS maglev train, and its guidance performance is crucial to the ability of curve-passing. Therefore, it is necessary to study the guidance force of YBCO bulks under a low-pressure environment. Based on the test system of magnetic levitation characteristics under low-pressure environments, the super-cooling state of liquid nitrogen is realized by the method of evacuation. The guidance force of YBCO bulks moving laterally above a Halbach permanent magnetic guideway was measured under different pressure values (100, 60, 40, 20 kPa). Results show that decreasing pressure is beneficial to improve the guidance performance of YBCO bulks. When the field cooling height (FCH) is under 35 mm, the guidance force increases with the decrease of the pressure. However, when the FCH is more than 35 mm, the guidance force decreases with the decrease of the pressure. Furthermore, decreasing FCH and pressure value can decrease hysteresis of guidance force and enhance the lateral stability of the HTS maglev system. [ABSTRACT FROM AUTHOR]

This paper mainly presents an ac loss numerical study of quasi-isotropic strands fabricated by second generation wires in cryogenic temperatures of 4.2 and 77 K. In order to estimate the ac losses accurately, a scaling relation of critical current density depending on themagnetic field andmagnetic field angle with wire is adopted in the model. AC loss contributions, including hysteresis and eddy current losses, are estimated in detail at 5-Hz magnetic field with amplitude range from 0.1 to 7 T. At low fields and 4.2 K temperature, hysteresis losses of quasi-isotropic strands are less than the eddy current losses (which mainly comes from the copper sheath), this situation is very different from the 77 K. Effects of the magnetic field frequency and orientation with a strand on ac losses are also particularly analyzed under different magnetic fields. The numerical results are helpful for overall understanding on ac loss characteristics of quasi-isotropic strands and are also useful for their applications in high magnetic field at low temperatures. [ABSTRACT FROM AUTHOR]

Western Superconducting Technologies Co. Ltd. (WST) has been keeping in the research and development of internal-tin Nb3Sn strand for higher performance level, for the future fusion reactor after ITER. Deformation optimization, Cu splits, and Sn spacers were applied to prepare Nb3Sn strand with higher Jcn and lower hysteresis loss, and the effect of these three factors on performance was investigated and discussed. Compared with the Nb3Sn strand for ITER, strand distortion was obviously reduced by deformation optimization and Jcn was improved, but at the same time hysteresis level was increased. To reduce the level of hysteresis loss, Cu splits were used to replace a few Nb filaments in each subelement. Cu splits could break the bridging Nb3Sn filament rings and as a sequence hysteresis loss was dramatically reduced along with the reduction of Jcn, which is attributed to low reaction degree of Nb filaments in the outermost subelements. Therefore, Sn spacers between the outermost subelements and the Ta barrier were added, and a 37-subelement structure was used to shorten the diffusion path of Sn. The reaction degree of the filaments was enhanced as well as Jcn . Finally, it could be concluded that a 37-subelement structure with Cu splits is effective to reduce the level of hysteresis loss and raise the level of Jcn . [ABSTRACT FROM AUTHOR]

In calculations for predicting the performance of high-temperature superconducting (HTS) cables, uniform physical and geometrical properties of the tapes are usually assumed. However, commercially available coated conductor tapes present a certain nonuniformity of their transport capability—namely their critical current—along the length. In addition, when coated conductor strands are compactly assembled to form a Roebel cable, their arrangement is far from the ideal one. In this work, we calculate the influence of Ic nonuniformities and of nonperfect strand alignment on the critical current of Roebel cables made of an HTS-coated conductor tape. For this purpose, we perform a statistical analysis using a recently developed and freely available open-source code to calculate the critical current of Roebel cables. We find that, for the considered cases, the nonuniformity of the strands’ Ic can have a significant impact on the final critical current of the cable, whereas the influence of the misalignment of the strands is rather low. [ABSTRACT FROM PUBLISHER]

ITER Nb3Sn strand quality verification tests require large quantities of precise measurements. Therefore, regular cross-checking between testing laboratories is critically important. In this paper, we present results from a cross-checking test of 140 samples between the National High Magnetic Field Laboratory, USA, and the University of Twente, The Netherlands. The tests comprise measurements at 4.2 K on critical current, residual resistance ratio, and hysteresis loss, while at room temperature the chromium layer thickness, Cu/non-Cu ratio, filament twist pitch, and diameter were determined. Our results show very good agreement between the two laboratories. The reasons for small random discrepancies are discussed. [ABSTRACT FROM PUBLISHER]

AC losses in high-temperature superconductors are an important design parameter for large-scale power applications. It is often necessary to have a metallic containment vessel to house the superconducting element in a closed-loop cryogenic system. This, however, produces additional ac losses due to induced eddy currents in the walls of the vessel. This paper focuses on the investigation and understanding of the induced eddy current loss in the containment vessel. The total ac losses of a 1-m yttrium barium copper oxide coil were experimentally measured in three different containment vessels. The predicted eddy current loss from finite-element modeling combined with the measured superconductor hysteresis loss demonstrated good agreement with the experimental results. This paper also includes the implications for practical design of commercial cryostat containment vessel for superconductor power applications to minimize ac losses [ABSTRACT FROM PUBLISHER]

We have developed and installed an 11 T Bi2Sr2Ca2Cu3Oy (BSCCO) insert coil for a 25 T cryogen-free superconducting magnet (25 T-CSM). The insert coil composed of a stack of 38 double pancakes was wound with DI-BSCCOTM Type HT-NX conductors which had high critical tensile strength of 400 MPa at 77 K. The insert coil is cooled by two two-stage Gifford-McMahon cryocoolers and the operation temperature of the insert coil is designed to be below 10 K. The insert coil has successfully generated 11.48 T without a background field and 24.57 T with a 14.0 T background field produced by outer low temperature superconducting coils in a 52 mm room temperature bore. Before the performance test, we fabricated and tested an R&D insert coil consisting of two double pancakes, which had the same configuration as the actual insert coil pancakes do, to confirm mechanical strength of the conductors [ABSTRACT FROM PUBLISHER]

This paper presents the results of calculation of ac HTS cables designs optimized by the values of hysteresis and eddy current losses. The superconducting elements of the cables are 2G HTS tapes. The program we developed and used allowed the variation of both the cable shape and its internal structure. There have been considered nonsectioned and sectioned cables having two variants of geometry—the axially symmetrical coaxial and extended rectangular cross-sectional shape. It has been shown that the internal structure optimization allows decreasing of ac losses in several times for both cross-sectional shapes. Due to the compensation of the perpendicular magnetic field component, the characteristics of flat three-phase cables turn out to be close of those with the axially symmetrical cross-sectional shape. In this case, the rectangular cross-sectional shape allows obtaining better mass, dimensional, and mechanical parameters and better cooling conditions of phases. The cables sectioning allows an essential reduction of ac losses. But, the latter is possible only when there is a uniform current distribution over the sections, i.e., at a very exact design calculation. [ABSTRACT FROM PUBLISHER]

Various critical state models have been developed to understand the hysteresis loss mechanism of high-temperature superconducting (HTSC) films. The analytic relation between the hysteresis lossx and the remanent field was obtained based on Bean's critical state model for thin films in the full-penetration case. Furthermore, numerical calculation of local hysteresis loops was carried out by Kim's critical state model. In this paper, we investigated local hysteresis losses for a GdBCO coated conductor by using low-temperature scanning Hall probe microscopy and reproduced the experimental results by applying the critical state model. Because of the demagnetizing effect in thin films, analysis of local hysteresis losses can be useful approach to understand of total hysteresis losses. [ABSTRACT FROM PUBLISHER]

Sandwich-type \MgB2\/\MgO\/\MgB2 Josephson junctions with sizes ranging from 0.5\ \mu\m \times 0.5 \ \mu\m to 10 \ \mu\m \times\break 10 \ \mu\m were fabricated using electron beam lithography. The junctions show critical current densities as high as 130 \kA/cm^2. The smallest of the junctions operated free of hysteresis below 4.2 K. They may be ideal for use in rapid single flux quantum circuits with no requirement for external shunt resistors. The 10- \mu\m junctions show good agreement with the expected Fraunhofer-like modulation of critical current with magnetic field; however, the smaller junctions show a sinusoidal modulation, indicating an anomalous current distribution that needs to be further investigated. Series arrays of Josephson junctions were made to quantitatively study the uniformity of junction parameters, which shows a 54% spread in critical current of a 100 junction array of 4- \mu\m junctions. [ABSTRACT FROM PUBLISHER]

To broaden the use of an adaptive resistive algorithm (ARA), we present a 3-D model able to reproduce the experimental magnetic moment loop for a finite-size superconducting strip in a perpendicular field. We also develop the same model by using $H$-formulation, to strengthen the ARA results. We find that 2-D models computed with the two different approaches, i.e., ARA and $H$-formulation, provide similar results, and both well compare to approximate analytical solutions. Then, we verify that the computed magnetic moment loop by using either 3-D numerical approaches reproduces the experimental curve, i.e., the magnetic loops of a commercial YBCO-coated conductor sample measured at 5 K. Instead, the 2-D numerical data need a scaling factor to match the experimental ones. The 3-D computations provide support to the hypotheses on the current surface profile that has been used to find the scaling factor. [ABSTRACT FROM PUBLISHER]

AC losses in an isolated superconducting round wire with a power-law electrical behavior produced by the combined effect of transverse alternating and rotating fields, i.e., an elliptical field, are investigated. The goal is to provide semianalytical expressions of the magnetization losses with a high enough reliability to be used in sizing code development or optimization methods. The fit expressions are based on data generated by means of a 2-D numerical model using the well-known and proved H-formulation. In the meantime, data processing allows for revealing a universal variable cn of utmost importance in magnetization loss calculation. This variable depends on the n-value of the power-law resistivity, and both the dimensionless magnetic field b^{\ast} and frequency f^{\ast}$. [ABSTRACT FROM PUBLISHER]

This paper presents a novel current sensor, which includes a giant magnetoresistance (GMR) chip, a toroidal magnetic core, and a feedback winding on the core. The mathematical model of the sensor was built, which was used to analyze the influence factors of the closed-loop current sensor. The closed-loop configuration with the magnetic core and the feedback winding improved the sensitivity of the sensor, eliminated the offset and drift related to temperature of the chip, and greatly reduced the error caused by magnetic hysteresis phenomenon. The simulation and test results showed that the novel current sensor has very low linear error (less than \pm 0.7%). The designed sensor can measure frequency of currents up to 100 kHz. The current sensor has high linearity with the range from 10 mA to 20 A. [ABSTRACT FROM PUBLISHER]

AC loss of \Nb3\Sn cable-in-conduit conductors (CICC) decreases after cyclic mechanical loading, but remains almost the same in case of Nb-Ti ones. It was observed during previous ITER CS, TF, and PF inserts tests in JAEA. The same phenomena have been detected on numerous ITER CS, TF, and PF short samples tested in the SULTAN facility. Experimental methods of ac loss investigation in JAEA-Naka and SULTAN were different, but the final results showed a good agreement. Analysis and numerical investigation of the present work were based on RF PF&TF CICCs SULTAN test results, theory of superconductivity, and our own physical and engineering understanding of evidence. Cyclic mechanical loading in both JAEA and SULTAN was initiated by electromagnetic force. In this paper, we attempt to explain why hysteresis, coupling, and mechanical loss decrease dramatically after cyclic mechanical loading and thermo-mechanical stress caused by WUCD (warm-up and cool-down) in \Nb3\Sn CICC. [ABSTRACT FROM PUBLISHER]

As giant magneto resistive (GMR) effect based current sensors are susceptive to stray magnetic fields, this paper proposes a GMR current sensor with a magnetic shielding. Magnetic shielding effectiveness and magnetic gain coefficient of the shielding are analyzed by finite element method (FEM), and some concerned parameters affecting the shielding effects are also discussed. In order to achieve accurate measurement for ac and dc, this paper proposed two methods for providing bias magnetic field. One method is using a coil winding and the other is using permanent magnet. Based on theoretical analysis and simulation results, a prototype was designed. Hysteresis effects on the sensor, the sensitivity of the GMR current sensor, and relative error of the measurement of the current sensor with and without magnetic shielding were tested and compared. The two methods for producing bias magnetic field were also tested and discussed. The designed GMR current sensor has the advantages of high sensitivity and accuracy, low nonlinear error (0.8%). It can measure currents from dc up to 200 kHz with the nominal primary current value of 20 A. [ABSTRACT FROM PUBLISHER]

To ensure accurate and consistent measurement of the physical and superconducting properties of the \Nb3\Sn and NbTi composite strand, a strand test facility benchmarking effort for the International Thermonuclear Experimental Reactor (ITER) was initiated in August 2008. Three rounds of benchmarking have been finished. The first round was referred to as the bronze-route \Nb3\Sn strand, while the second and third benchmarking were referred to as Internal Tin \Nb3\Sn and NbTi strand, respectively. As the referenced lab of the Chinese Domestic Agency, the superconducting strand test lab from the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) participated in all the three rounds of benchmarking. The benchmarking includes tests for critical current (IC), n-index, hysteresis loss, Residual Resistivity Ratio (RRR), strand diameter, Cu fraction, twist pitch (TP), twist direction, and metal plating thickness. The results from ASIPP were acceptable except for the RRR measurements on \Nb3\Sn strands for the first and second benchmarking. Improvements have been made mainly for RRR and TP measurements, and the test reports for the third benchmarking were approved by the ITER organization. The test facility and test results were presented in this paper. [ABSTRACT FROM PUBLISHER]

The hysteresis loss (Qhyst) of a conductor is a very important parameter for magnet design. Due to the anisotropy of the REBCO conductor, its Qhyst strongly depends on magnetic field orientation. During a field ramp of a REBCO magnet, at locations where radial field component is significant, Qhyst may be large. This may significantly reduce the design temperature margin and increase the liquid helium consumption. Therefore, it is very important to measure the field and field angular dependence of Qhyst of the REBCO conductor. In this paper, we measured Qhyst of a small REBCO sample by vibrating sample magnetometry. The measurements were performed in a resistive magnet at the NHMFL with magnetic fields up to 35 T. The magnetization of a 1\times 1\ \mm^2 sample was measured in different fields, field orientations, and temperatures. The implication of our experimental results on the REBCO magnet design is discussed. [ABSTRACT FROM PUBLISHER]

Considerable attention has been paid in the last years to the development of fast-cycled superconducting magnets for future accelerators, leading to the design and construction by INFN and GSI of a 3.8-m-long prototype of a 4.5 T, 1 T/s, dipole magnet, for the SIS300 synchrotron of the FAIR facility (Darmstadt, Germany). This ramp-rate is 20–100 times higher than the one used in other superconducting synchrotrons like RHIC or LHC. Being operated at rather large dI/dt, these magnets are subjected to a wide spectrum of ac dissipation, taking place in the superconductor as well as in the metallic components of the mechanical structure, requiring the development of specialized superconducting cables and a careful consideration of the other aspects of the structural design. Between July and September 2012, the dipole magnet prototype has been subjected to a test at LASA laboratory (INFN Milan, Italy), during which it was successfully operated at current ramp rates as high as 0.7 T/s (the power supply limit). In this paper, we describe the V-I apparatus used to assess the dissipations within the magnet during the ac regime, the measurement results, and their comparison with the values expected from the design and on the basis of superconducting cable qualification results. [ABSTRACT FROM PUBLISHER]

Cables in superconducting magnets are subjected to field-dependent losses, i.e., induced interstrand and interfilament coupling losses, and superconductor hysteresis losses. For the two kinds of induced eddy currents, analytical and numerical models are available, allowing calculating the dissipated power under various operating conditions. For the losses stemming from the superconductor magnetization, the literature only gives formulas for the dissipated energy over closed excitation cycles. We derive an expression for the instantaneously dissipated hysteresis losses during an arbitrary ramp profile using a simplified geometry and hysteresis model. This allows estimating the losses dissipated in nonclosed excitation loops. [ABSTRACT FROM PUBLISHER]

Operated under high magnetic field (>11 T), the toroidal field (TF) system consists of complex conductors using \ Nb3{\ {Sn}} as superconducting material. According to the strand requirements for the ITER TF conductor, bronze processed \ Nb3{\ {Sn}} strands with high superconducting performance have been manufactured using high tin content bronze at WST. The studies on filament diameter, diffusion barrier, sample heat treatment and annealing temperature have been carried out to enhance \ Nb3{\ {Sn}} strand properties. The results of these investigations have been presented. The result indicates that the different filament diameter has a weak influence on the critical current (Ic) value for the different reaction degree. In the manufacturing process the annealing temperature should be kept below 500 ^\circC to realize a high n value. The continuous \ Nb3{\ {Sn}} layer formation on the internal surface of the barrier causes a considerable increase of hysteresis loss when single Nb barrier is used. There is almost no difference of Ic, hysteresis loss and grain morphology for two heat treatments: ITER heat treatment cycle B and WST heat treatment cycle. [ABSTRACT FROM PUBLISHER]

The development of domestic HVDC transmission system needs the HVDC transformer to perform better. A large amount of higher harmonics will be generated in the load current when the transformer works in a converted way. Due to this, the eddy current field is a nonlinear and non-sinusoidal one. Based on Visual Basic 6.0 and MagNet, special software for magnetic leakage field analysis and stray loss calculation was written. Using the special software, the distribution of magnetic leakage field was studied and the stray loss of the transformer was calculated. [ABSTRACT FROM PUBLISHER]

In the present, the potential of applying the high temperature superconducting (HTS) technology to rail traffic is increasingly being noticed and gaining much interest. In practical applications, the HTS maglev vehicle may operate a “Z” type movement due to external disturbances such as air currents, railway defects and so on. This paper presents experimental results of this type behavior by studying multi-seeded bulk YBaCuO samples operating in a “Z” type movement with different lateral displacements above a permanent magnet guideway (PMG) in the field-cooling mode. The torque is found to increase with the lateral displacement increasing while torque is zero and has a little change when the lateral displacement is 5 mm and 10mm, respectively. In the longitudinal direction, hysteresis increases with lateral displacement increasing. [ABSTRACT FROM PUBLISHER]

Short sample HTS power cable composed of multiple 344C-2G strands and designed to energize a fast-cycling dipole magnet was exposed to a sweeping magnetic field in the (2–20) T/s ramping rate. The B-field orientation toward the HTS strands wide surface was varied from -4^\circ to 8^\circ, in steps of 10. The test arrangement allowed measurements of combined hysteresis and eddy current power losses of the cable assembly. For the validity of these measurements, the power losses of a short sample cable composed of multiple LTS wire strands were also performed and compared with the known data. The test arrangement of the power cable is described, and the test results are compared with the projections for the eddy and hysteresis power losses using fine details of the test cable structures. [ABSTRACT FROM PUBLISHER]

JT-60SA is a fusion experiment designed to support the operation of ITER and to investigate how best to optimize the operation of fusion power plants that are built after ITER. The toroidal field (TF) coils uses the Cable-in-conduit Conductor (CICC) with NbTi superconducting strands. The TF coils will operate at with 25.7 KA @5.65 T, 4.9 K. Western Superconducting Technologies Co., Ltd. (WST) has studied two types of NbTi superconducting strands for the JA-60SA TF coils. The strands choose the internal CuNi alloy for the internal resistive barrier, which is expected to calibrate and control the inter-strands resistances and to better current distribution between strands in CICC. The strand samples were tested in the range of 4 \sim 11 T magnetic field at 4.22 K for critical current, and 5.7 K \sim 6.4 K at 5.65 T for current sharing temperature. This paper presents the results on critical current(Ic), critical current density (Jc), current sharing temperature (Tcs), and hysteresis loss of the strands. [ABSTRACT FROM PUBLISHER]

The sensitivity of superconducting magnets to AC losses is well known. If superconducting magnets are this sensitive to AC fields, why not use AC fields for magnet protection, and in particular, for internal energy dump when a quench has been detected? The answer is the large reactive power needed to provide the rate of change of the fields required to quench of a large fraction of the magnet. In this paper we describe a novel approach where quench protection secondary windings external to the magnet are used to minimize the power to initiate the energy dump. The main requirement of these secondary windings is that the mutual inductance between the primary winding and the protection secondary windings has to be small, ideally zero. One means to provide for zero mutual inductance between the protection secondary winding and the primary winding is by designing a protection secondary winding that produces AC fields that everywhere in the volume are normal to the fields produced by the primary winding. Alternatively, appropriate windings can be made so that the coupling in one region is the opposite to that of another region, with zero total mutual inductance. The latter approach results in low voltages at the leads, but could result in high voltages within the coil. We describe several circuit topologies applicable to solenoidal and toroidal windings that satisfy these requirements. Calculations of the heating due to AC fields are presented, including eddy current heating in cable-in-copper-channel conductors. If the quench inducing coil is optimally designed and powered, the hysteresis of the superconductor dominates the heating. Thus, as a portion of the superconducting magnet quenches, the heating power shifts to those zones that are not yet in the current-sharing regime. This approach is an alternative to the use of resistive heating elements, which need to be placed on, or embedded in, the winding pack. [ABSTRACT FROM PUBLISHER]

We investigated the characteristics of transport current loss against distorted current with odd-order harmonic component using a Bi2223 short sample conductor. We measured the transport current loss against the distorted current with the 3rd, 5th, or 7th harmonic as a function of the amplitude of each harmonic current. The transport current loss per cycle of fundamental frequency against the distorted current was independent of the fundamental frequency and was compared with the sum of transport current losses against the sinusoidal current with the amplitude of each harmonic current component obtained by Fourier analysis. Fair agreement was obtained in the distorted current with the 3rd harmonic, while a big difference was observed in the distorted current with the 5th or 7th harmonic. Independent of harmonic order, the transport current loss against the distorted current was almost the same as the sum of the transport current losses against the sinusoidal current with the amplitude of the distorted current corresponding to a major hysteresis loop and the amplitude of the small rise and fall of the distorted current corresponding to a minor hysteresis loop that can be directly estimated from the distorted current waveform. [ABSTRACT FROM PUBLISHER]

The amount of hysteresis losses is a key parameter for the design of high-temperature superconducting (HTS) transformers. Leakage field, particularly its radial component, decreases critical current and increases hysteresis losses in HTS tapes. Prior art proposed the adoption of two auxiliary windings to an HTS transformer for minimizing the leakage flux densities by generating a field that opposes the leakage field, thereby reducing the hysteresis loss in an exemplary HTS transformer. In this paper, a proposed design will become prominent by obtaining a variant of distributive ratios via an intelligent choice of the secondary–primary–secondary–primary turn ratios in the neighborhood of the auxiliary windings to produce magnetic poles canceling or diminishing the corresponding leakage fields to the maximum effect. The mentioned schemes require accurate, yet efficient, advanced numerical techniques using 3-D solver of FLUX software for a precise calculation of the leakage flux density and hysteresis losses in an exemplary HTS transformer as a precious guide. [ABSTRACT FROM AUTHOR]

A 40-T hybrid magnet under construction at the High Magnetic Field Laboratory of the Chinese Academy of Sciences will use cable-in-conduit conductors for its superconducting outsert. The design necessitates the use of high current density (Jc) \Nb3\Sn strands (Jc \geqq \2100\ \A/mm^{2} at 12 T/4.2 K). The high Jc restacked-rod-processed \Nb3\Sn strand from Oxford Instruments Superconductor Technology was selected as one of the candidate strands. A series of tests was carried out to qualify the strand performance. Tests mainly included magnetization and critical current measurements as a function of axial strain, magnetic fields, and temperature. The test results are presented and discussed. [ABSTRACT FROM AUTHOR]

The current carrying capacity of different design internal tin strands at high magnetic fields was investigated. Two high critical current density internal tin Nb3Sn strands with different level of mechanical properties have been designed. The increase of mechanical strength has been attained by replacing part of the stabilizing copper by strengthening elements made of “in situ” nanocomposite Cu-Nb rods. The analysis of the mechanical properties of the strands in virgin state and after the reaction heat treatment has been done. The microstructure of strands components including Nb3Sn filaments has been investigated. The results of current carrying capacity measurements of 0.6 mm diameter strands in magnetic fields up to 20 T (4.2 K; 0.1 \muV/cm) and hysteresis losses measurements (\pm3 T cycles) are presented. It was shown that for the strand with enhanced mechanical strength the non-Cu critical current densities attained were 2580 A/mm^2 and 235 A/mm^2 at 12 T and 20 T, respectively, and for the strand without strengthening elements the non-Cu critical current densities were equal to 2250 A/mm^2 and 500 A/mm^2 at 12 T and 20 T, respectively. The correlation between the microstructure and superconducting properties of the different strands designs are discussed. [ABSTRACT FROM AUTHOR]

The results of investigations of first 500 kg Nb3Sn bronze strand are presented. This batch of strands was meant for the production of 100 m of Toroidal Field Conductor in the frame of fulfillment the Phase II of Procurement Arrangement between Russian Domestic Agency and International Organization ITER. In order to provide the industrial-scale production of strands design documentation and all necessary quality assurance documents were developed. The developed industrial technology of Nb3Sn strand production was applied in Joint Stock Company «Chepetsky Mechanical Plant» (JSC «ChMP»). Strands were produced in JSC «ChMP» from final billets with diameter of 203 mm. The microstructure investigations of produced strands were performed before and after diffusion annealing by optical microscopy, X-ray microprobe analysis. Mechanical properties of annealed Nb3Sn strands were investigated. Current-carrying capability of Nb3Sn strands at 12 T, 4.22 K were studied. It was shown, that all produced strands met all the requirements, in particular Ic was from 202 to 220 A; hysteresis losses were from 165 to 194 mJ/cm^3 (\pm 3 T ). [ABSTRACT FROM AUTHOR]

Magnetization measurements are relevant tests for the characterization of superconductors. Practically they are the only measurements that allow estimating the critical current density at low fields of low temperature superconductors, the effective filament size and the hysteresis losses. For this purpose CERN, in collaboration with the University of Geneva, has carried out magnetization measurements on five types of \Nb3{\Sn} wires: three bronze route strands used in the ITER project; one Powder In Tube (PIT) and one Internal Tin (IT) wires used for developing next generation accelerator magnets. The field dependent magnetization has been determined using three setups: a Vibrating Sample Magnetometer (VSM), a Superconducting Quantum Interference Device (SQUID) and a special system used for the production control of LHC strands. Samples of different lengths have been tested to check the different coupling between the filaments. Unexpectedly, it was found that the magnetization of the tested bronze wires was strongly dependent on the sample length. In this paper, the results, which were obtained for different type of strands and sample lengths, are reported and compared. [ABSTRACT FROM AUTHOR]

About 450 km of high JC Nb3Sn wires have been procured for the construction of two series-connected hybrid magnets by the National High Magnetic Field Laboratory (NHMFL). In addition to the quality assurance tests by the wire manufacturer, a receiving quality assurance inspection with a predetermined sampling frequency is carried out at the NHMFL. These tests include wire diameter, twist pitch, Cu/non-Cu ratio, IC, residual resistance ratio, hysteresis loss, and IC strain dependence. In this paper, the test procedures are described and the test results are presented. Based on these test results, all the wires have been accepted. [ABSTRACT FROM AUTHOR]