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One of the most challenging issues in super conducting-bearing technology is the rotor's stability, which is closely related to the levitation configuration. Establishing a stable and fixed position of the rotor requires strong stabilizing forces among the bulk superconductor and permanent or electromagnets. The proposed configuration for the superconducting magnetic bearing in this paper consists of a permanent magnet on the rotor and a combination of a cylindrical bulk superconductor and a ring permanentmagnet base. The load-carrying capability of the proposed bearing configuration is analyzed in terms of the vertical force on the rotor as a function of the vertical and lateral displacements. In addition, the lateral stability mechanism is evaluated by determining the lateral forces on the rotor as a function of the vertical and lateral displacements. The forces on the rotor are determined with a quick and effective calculation by usingMATLAB for various design configurations based on the considerations of the cooling procedure of the superconductors, the Amperian current approximation, and the frozen-image model. According to the results of the analysis, for the same levitation heights the proposed bearing design having ring permanentmagnet in the base provides levitation force higher than that of without having the ring permanent magnet. The present levitation configuration provides better clearance between the rotor and stator in the bearing. [ABSTRACT FROM AUTHOR]

Superconducting magnet (SM) plays a crucial role in the success or failure of a superconducting generator. The SM of a 50 kW superconducting synchronous generator (SSG) was studied in this paper. Magnesium diboride superconducting wires are employed to wind the SM. First, the initial structure of SM is designed by finite element modeling. After which an approach based on response surface methodology and particle swarm optimization is used to optimize the initial structure of SM. Finally, in order to verify whether the designed SM conforms the requirements of the 50 kW SSG, the SM is made and tested by the optimized size. The results indicate that the designed SM can better meet the requirements. [ABSTRACT FROM PUBLISHER]

Highly efficient liquid hydrogen storage system is studied with magnetic levitation using high-temperature superconducting (HTS) coils. The system also has high safety in case of emergency, such as an earthquake, with a seismic isolation to absorb vibrations provided by HTS levitation coils setup on the ground side. In such an emergency case, it is considered that a large amount of ac losses are generated in HTS coils, and the winding temperature may rise to lead to a coil quench. In this study, the self-oscillation-type heat pipe (OHP), whose thermal transport property is much greater than that of solid thermal conduction, is used to cool the coil windings. As a result, an HTS coil equipped with an OHP cooling system can be realized, supporting both low heat loads in the usual operation and high heat loads in an emergency. [ABSTRACT FROM PUBLISHER]

A superconducting magnetic bearing can levitate a rotor without contact. However, the rotor can whirl with large amplitude. To reduce the whirling amplitude, we focused on an electromagnetic shunt damper that is appliable to a rotor system. In this paper, an analysis considering influence of magnetic flux density distribution on dynamics of the rotor was carried out. From linearized and nondimensionalized governing equations, we obtained one parameter that determines the damper's effectiveness. Further, numerical calculation was performed and the optimum value concerning the dimensions of the electromagnetic shunt damper was obtained. [ABSTRACT FROM PUBLISHER]

The route to 30 T NMR endorsed by a recent National Academy report [1] clearly still has many challenges to achieve a high stability and a homogeneous high-temperature superconducting (HTS) insert magnetic field. As the only HTS conductor with round wire (RW) geometry, Bi2Sr2CaCu2 O8-x (Bi-2212) RW conductor is very attractive for nuclear magnetic resonance (NMR) magnet applications. At present, an NMR quality demonstration magnet with Bi-2212 RW wound insert coils is under development at the National High Magnetic Field Laboratory. The target of this demonstration magnet is to generate a total field of 23+ T with ppm level homogeneity. Since Bi-2212 coils require wind-and-react technology, our initial major concern was that large Bi-2212 coils might deform during the typical partial melt Bi-2212 heat treatment (HT) due to their large self-weight. To experimentally mimic the HT of large Bi-2212 coil, several small test coils were heat treated under deadweight loads. After 1 bar Bi-2212 full reaction, these coils were characterized in terms of coil geometry, transport critical current (Ic) properties, oxygenation status, and insulation performance. Coil geometry and individual wire shape were in fact not distorted, nor was transport property degradation induced by mechanical loading. Uniform oxygen equilibration was achieved in these coils even though they were coated with dense oxide insulation. However, although the TiO2-based insulation coating was well preserved on the wire surface, several coils developed electrical shorts. [ABSTRACT FROM PUBLISHER]

This paper proposes a new high-temperature superconductor (HTS) dual-rotor flux-switching machine for direct-drive wind energy conversion. The key is to adopt dual-rotor structure to improve utilizations of the HTS excitation field and the machine space, thus achieving a high power density. Also, the HTS excitation can easily achieve flexible flux regulation to keep armature voltage constant under time-varying wind speeds. The operation principle, with emphasis on the effect of relative position of both rotors on the magnetic circuits, is described in details. And the initial machine design, especially the split ratio optimization, has been done. By using the finite element analysis, the machine performances are analyzed, and its validity is verified. [ABSTRACT FROM PUBLISHER]

Triaxial HTS power cables are the optimal solution for low and medium voltages. This design permits to save expensive HTS conductor and to increase the power density transmitted. They could be used at medium voltages ∼10–20 kV for distribution grids. At relatively low voltages (<1–10 kV), triaxial cables could be used for ship propulsion systems or in electrical aircraft, where higher voltages are prohibited due to operational conditions. Prototypes of HTS “triaxial” cables made of both Bi-2223 and ReBaCuO HTS wires have been developed and tested in the Russian Scientific R&D Cable Institute. The calculations to optimize the cables with three superconducting layers and outer copper shield have been performed. The optimal parameters have been determined. The Bi-based 10-m cable has been inserted in a full-size flexible cryostat with current leads developed and has been tested at dc and ac conditions. The 4-m ReBaCuO cable has been tested in a laboratory cryostat and tested at dc and ac conditions also. AC tests of both cables were performed at different frequencies from ∼37 to ∼400 Hz. The cables designs, test results, and their analysis are presented. [ABSTRACT FROM PUBLISHER]

High-temperature superconducting (HTS) magnet made out of coated conductors (CCs) is considered as a possible alternative for conventional LTS magnet used in MRI and nuclear magnetic resonance (NMR) because of the high critical temperature and excellent performance under strong field. However, due to the difficulty of fabricating the superconducting joints of CCs, the HTS magnet made of CCs cannot yet operate in persistent current mode (PCM). In this study, a new type of PCM coils made of CCs, called double-slit coil, is developed to fabricate a pair of Helmholtz coils with an inner diameter of 50 mm. The angle deflection of the magnetic field trapped by the double-slit coil can be reduced due to its symmetric structure on the z-axis and therefore improve the field homogeneity. Both of z-axial and y-axial components of magnetic field distribution along the z-axis is measured at 77 K by a motor-driven hall probe with an automatic data acquisition system. The result shows that the double-slit Helmholtz coils perform similarly to circular coils on the z -axial component and the y-axial harmonic component can be reduced to less than 0.2% of the total trapped magnetic field. Finally, a conceptual structure of HTS shielding coils applied in MRI/NMR. [ABSTRACT FROM PUBLISHER]

There is an urgent need for the fault current limiter to guarantee the stability of the dc system. For this reason, the improved inductive superconducting fault current limiter (SFCL) is designed and its working principle is addressed. By analyzing the transient characteristics of the dc fault in modular multilevel converter based dc system, the current-limiting effects of the proposed SFCL are studied in detail. According to the current-limiting requirements and the coordination among the converter, the fault current limiter and the dc circuit breaker, the desired impedance of the SFCL is discussed in this paper. Finally, the effectiveness and correctness of the analyses have been verified by the simulation results based on the PSCAD/EMTDC simulation [ABSTRACT FROM PUBLISHER]

With recent challenges in developing high-temperature superconductor coils using rare-earth barium copper oxide (REBCO) conductor, particularly critical current degradation in a fully wet wound coil using traditional epoxy, we present engineering stress analysis and new winding approaches in its coil fabrication in order to produce high quality coils. Its implementation, however, necessitates novel approaches and nonconventional considerations. This paper first calculates stress and analyzes stress concentration in the REBCO coil in processes of coil winding and thermal cycling. Thus, a thin film layer has been added to reduce the stress concentration on the coil winding. Second, it describes the critical current anisotropic properties and apply to a Helmholtz coil design to draw attentions to develop a full matrix of Ic(B, T, φ) data for various magnet designs. In the coil fabrication, it introduces a dry winding method with stainless steel cowind (metallic insulation) that has been applied and successfully delivers high quality high temperature superconductor (HTS) coils. Additionally, it tries a fully wet winding approach but employs alternative epoxy—Araldite and no degradation has been found after a few thermal cycles. [ABSTRACT FROM PUBLISHER]

Superconducting current-limiting transformers offer an effective current limitation and recovery-under-load characteristics; they are more compact and have a lightweight design and a reduced short-circuit impedance. Several designs for superconducting current-limiting transformers have been developed and proposed by researchers over the last two decades. However, less research work was devoted to effective current limitation of superconducting transformers in combination with recovery under full or under partial load. In this paper, we present the process of manufacturing a superconducting transformer demonstrator with current limitation and recovery-under-load capabilities. The demonstrator consists of a laminated iron core and a normal conducting 20-kV primary winding, both operated at the room temperature. 2G REBCO tapes are used for the secondary winding, which is operated at 1-kV nominal voltage. In order to keep the secondary winding at cryogenic operation conditions at 77 K, a vacuum insulated fiber reinforced plastics cryostat was designed and manufactured. [ABSTRACT FROM PUBLISHER]

High-temperature superconducting (HTS) power cable has significant merits of compactness and large power transmission capacity. Although the stability of the HTS cable system was verified by in-grid operation, the verification of its safety and reliability against various accidents is required for practical use of this system. A ground fault accident is one of the typical accidents of a conventional cable. If this fault occurs by breakdown of the dielectric layer, the generated arc energy is dissipated into the environment in various forms. As a result, the safety of the public may be jeopardized. Arc energy relates to arc voltage, which is dependent on the inherent physical properties of the faulted equipment. The use of coolant and the structure of the HTS cable differentiate it from a conventional cable, so it should be verified how these differences influence the arc voltage. Accordingly, ground fault tests using the HTS cable were conducted and the arc voltages were compared to that of a conventional cable. The results obtained proved that the arc voltage on the HTS cable is similar to that of a conventional cable, in spite of the differences concerning the use of coolant and the cable structure. [ABSTRACT FROM PUBLISHER]

This paper focuses on conceptual design and electromagnetic analysis of a single-phase high-temperature superconducting (HTS) power transformer with a capacity of 300 kVA by using GdBCO tapes, which is one-third model of a 1 MVA/10 kV/0.4 kV HTS transformer. The conceptual design consists four parts: iron core, HTS windings, current lead, and cryostat. In the electromagnetic optimization of the 330 kVA HTS transformer windings via finite element method, the influence of winding configurations on the radial magnetic field and the current nonuniformity are considered. The details about the design and optimization of radial magnetic field will be discussed in this study. [ABSTRACT FROM PUBLISHER]

In the past years, different superconducting levitation systems were developed around the world. Most projects focused on optimizing the flux density in the working space of the superconductor in order to maximize the levitation force of the system. In general, these systems use tracks with permanent magnetic Halbach arrays or combine permanent magnets with steel yokes to maximize the usable flux density. Therefore, none of these tracks can easily be switched off to allow a safe crossing or to build a fast turnout switch without moving parts. A new track was designed containing permanent magnets and a YBCO-tape-coil to realize a fast switchable track. In this concept, the permanent magnets provide the flux used for levitation, whereas the coil controls the flux in the space above the track, where levitation usually takes place. The magnetic behavior of this new design was studied and improved with two-dimensional (2-D) and 3-D simulations. Afterwards, a demonstrator was built on which the induced magnetic field was measured in the different operation modes. The results of the measurements and the simulations indicate that the flux density above of the track might be controlled by the coil current. It was proven that the new track design generates magnetic fields comparable to the standard permanent magnetic track, whereas only residual fields are measured in inactive mode, which can be further reduced with negative coil currents. [ABSTRACT FROM PUBLISHER]

The use of bulk high-temperature superconductor material has been proposed for various noncontact transportation systems.  Commonly, such systems use permanent magnets to achieve levitation of a vehicle housing bulk superconductors, with motive force provided separately.  Recent work has focused on using electromagnets to provide both the levitation and the motive force. Through energizing appropriately placed electromagnets in a correct pattern, straight line travel and rotation across a horizontal plane are possible. However, significant overshoot and instability can be incurred during motion events, leading to changes in the flux pinning state and misalignment of a vehicle. This paper proposes the design of a planar array of electromagnets and an energization pattern that achieves controlled rotation. Straight line travel is also achieved. Thus, using the proposed drive system, straight-line travel as well as rotation of a levitated vehicle across a horizontal plane is possible. Experimental verification is provided. [ABSTRACT FROM PUBLISHER]

The Michigan State University cyclotron gas-stopper magnet generates a strong focusing cyclotron magnetic field that permits an ion beam of up to 100 MeV/u to enter the magnet and have most of its energy reduced by low-pressure helium gas. The magnet has two superconducting coil cryostats mounted within warm iron poles and a warm split iron return yoke. The coils are connected in series using room temperature cables. The peak magnet stored energy is 3.5 MJ. The magnet has been tested to its full operating current of 180 A. During tests, the magnet discharged inadvertently three times. Two low-current discharges caused the magnet current to decay through the power supply system. A discharge at 180 A quenched the magnet, because the quench protection system caused the magnet to discharge across a 1.25-Ω resistor. This fired the cold quench protection diodes within the cryostat, quenching both coils. The magnetic field in the gap was measured as the magnet discharged. For the two low-current discharges, the magnetic field followed the current in the external magnet circuit. During a quench, the magnetic field decay rate was much slower than the external circuit current decay rate. [ABSTRACT FROM PUBLISHER]

In the latest design studies of superconducting magnetic energy storage (SMES) systems, the emphasis was put on the electromagnetic design of SMES magnets without giving due attention to the electrical design with a view to eliminating the overvoltage problem. The power conditioning system (PCS) interfaces with the superconducting magnet and the ac system through an electrical connection. With a pulse-width modulation converter usually adopted in the PCS, the high-frequency overvoltage problem is even more serious. Therefore, electrical design based on voltage distribution analysis and protection measures should be taken into account during the SMES design. This paper first gives transient models of PCS, SMES, and the connecting cable in a systematic view. Later on, a design flow path containing both the electromagnetic design and the electrical design is presented. Adopting the proposed design method, one design plan of a 1 MJ HTS SMES is chosen and conclusions are drawn on its optimal comprehensive design plan. [ABSTRACT FROM PUBLISHER]

INFN is developing at LASA lab (INFN Milano, Italy) the prototypes of five corrector magnets, from skew quadrupole to dodecapole, which will equip the high-luminosity interaction regions of the High Luminosity-LHC. These magnets are based on a superferric design, which allows a relatively simple, modular, and easy to construct magnet. This activity takes place within the framework of a collaboration agreement between CERN and INFN. The first prototype, a sextupole, has been assembled in early 2016. We present here the results of the cold test, including the training performed at 4.2 K and the qualification at 2.2 K. We report also on the overall experience gained during its construction and test. An important aspect is represented by the analysis of the manufacturing tolerances of the mechanical pieces and the alignment accuracy achieved. These results will serve as a basis for the design of the next magnets, the octupole, and the decapole. Other important results concern the cold performance of the coil-to-coil electrical joints (especially critical in a magnet with a large number of coils), dynamic inductance measurements and quench studies. [ABSTRACT FROM PUBLISHER]

For the application of Re1Ba2Cu3O7-δ (REBCO: RE such as Y, Gd, and Eu) superconducting tapes to large-scale magnets, an enhancement of current capacity is required for magnet protection. In this study, a configuration of parallel conductors were introduced, and the current-sharing properties of three-strand parallel conductors wound into a pancake coil were investigated. An equivalent resistance exists even for a much smaller current than the critical current Ic. This should influence the current sharing among the tapes even if inductances are balanced by transposition. Uneven current sharing could lead to a fatal problem in the uniformity of a produced magnetic field, which is usually on the order of ppm. In this paper, every branch current was evaluated by numerically solving the circuit equation. As a result, it is shown that, in the case where the constituent tapes are different in Ic and n values, this should influence the current sharing among the tapes even if both the inductances and joint resistances are balanced among the tapes. An unbalance is serious when the difference in Ic and the n value is large. In addition, an unbalance increases as frequency decreases. The results suggest that uniformity in Ic and the n value of the REBCO tapes is important for the development of MRI magnets. [ABSTRACT FROM PUBLISHER]

We presented a compact and high-power dual-mode high-temperature superconducting filter with double-strip resonator (DSR) for transmit filter applications. The DSR structure reduces not only the current concentration at the edges of the resonator compared with that of a conventional microstrip resonator due to the increase of the effective film thickness but also the coupling between resonators. Thus, the DSR structure contributed not only to enhance the power handing capability of the filter but also to the size reduction of the dual-mode filter. An electromagnetic simulator based on the moment method was used to design and investigate the filter. A double-strip four-pole dual-mode square patch filter with a 5.0-GHz center frequency and 100-MHz (2%) bandwidth was designed. A compact (25 mm × 25 mm) filter was fabricated using YBa2Cu3Oy thin film on an Al2O3 substrate. The measured frequency response of the filter was in reasonable agreement with the simulated one. Power-handling capability of the filter was more than 41.7 W (46.2 dB·m) at 70 K. [ABSTRACT FROM PUBLISHER]

Five solenoid-based focusing lenses designed for use inside the SSR1 cryomodule of the PXIE test stand at Fermilab have been fabricated and tested. In addition to a focusing solenoid, each lens is equipped with a set of windings that generate magnetic field in the transverse plane and can be used in the steering dipole mode or as a skew quadrupole corrector. The lenses will be installed between superconducting cavities in the cryomodule, so getting sufficiently low fringe magnetic field was one of the main design requirements. Beam dynamics simulations indicated a need for high accuracy positioning of the lenses in the cryomodule, which triggered a study towards understanding uncertainties of the magnetic axis position relative to the geometric features of the lens. This report summarizes the efforts towards certification of the lenses, including results of performance tests, fringe field data, and uncertainty of the magnetic axis position. [ABSTRACT FROM AUTHOR]

Uniform, graded and spaced arrays of 3 μm triangular antidots in pulsed laser deposited YBa2Cu3O7 (YBCO) superconducting thin films are compared by examining the improvements in the critical current density [ABSTRACT FROM AUTHOR]

A cryogen-free 20 T superconducting magnet with a 52 mm room-temperature bore was developed and installed in Tohoku University in 2013. This magnet consists of a Bi2223 insert coil, which generates 4.5 T, and outer low-temperature superconducting (LTS) coils. Both coils were cooled by a GM/JT cryocooler with 4.2 W-class cooling capacity at 4.3 K. To generate a higher magnetic field, a new cryogen-free 25 T superconducting magnet using a REBCO insert coil, which generates 11.5 T, and new outer LTS coils is now under development. The magnetic field contribution of this REBCO insert coil is considerably higher than that of the previous Bi2223 insert coil, and the ac-loss of the insert coil during field ramping rises to approximately 9.7 W. The LTS coils have to operate at about 4 K, but the REBCO coil can operate at various temperatures above 4 K. In addition, the cooling capacity of a GM cryocooler is greater than that of a GM/JT cryocooler around 10 K. Thus, the REBCO insert coil is cooled to about 10 K by using two GM cryocoolers, independently of the LTS coils, which are cooled by two GM/JT cryocoolers. To protect the cryocoolers from the leakage field of the magnet, the two GM cryocoolers cool circulating helium gas through heat exchangers, and the gas is transported over a long distance to another heat exchanger provided for the REBCO insert coil. The maximum temperature of the REBCO insert coil was calculated under the most severe condition where an insert coil ac-loss of 9.7 W was generated continuously. And it was confirmed to be less than the target maximum temperature of 12 K. [ABSTRACT FROM PUBLISHER]

We have developed a conduction-cooled superconducting magnet system (CCSMS) using a low-temperature superconducting (SC) coil. The CCSMS consists of several metal components in contact with each other between the cryocooler and SC magnet. The thermal contact resistance (TCR) occurring at these metal interfaces may affect the CCSMS. Therefore, accurate measurement of TCR is essential for the design and development of CCSMS. We fabricated a TCR measurement system using a cryocooler as a heat sink. The TCR was calculated using the temperature gradient across the metal interface measured in the steady state. The temperature distribution along the thermal link in the CCSMS was estimated using the measured TCR and compared to the experimental values. The influence of surface roughness on the temperature distribution in the CCSMS is also discussed. [ABSTRACT FROM AUTHOR]

The authors presented practical fabricated specifications of a prototype 10kW class high-temperature superconductor (HTS) direct current (DC) induction heating machine and analyzed its operational characteristics including the system's efficiency and the temperature distribution of the aluminum billet in detail In this paper, we discussed the fabrication process and focused particularly on the practical operating results of the HTS DC induction heating machine. The major operating characteristics of the HTS magnet under each stage were analyzed in detail. Detailed efficiency was investigated through the measuring of the realtime motor input and the billet temperature. Through a monitoring system, critical parameters were measured in real-time operation. The total heating time to 500 C of the billet's temperature was 400 s at 0.25 T at the center of the billet. These research outcomes are expected to be useful for the commercial design of a large-scale 2G HTS DC induction furnace for industrial fields. [ABSTRACT FROM AUTHOR]

The superconducting magnet is successfully installed on the 18-GHz ECR ion source at the National Fusion Research Institute (NFRI). The ECR ion source will be used as a multi-application source of highly charged ions and their interaction with matter. The magnetic system compromises of four superconducting coils sets for the axial mirror field and a permanent hexapole magnet for the radial mirror field. The previous superconducting magnet with a single cryocooler (1.5 W at 4.2 K) had been designed to reach peak mirror fields of 2.2 T in the injection and 1.5 T in the extraction regions (You et al., Rev. Sci. Instrum. 85, 02A916, ). However, it has not been successful in reaching the designed value (125 A) of current excitations; magnet coils have been shown to repeatedly quenched around 50-60 A of current ratings. After a detailed analyses and inspection, we found several weak points to be the possible cause of quenching. In this presentation, we describe important upgrades and technical improvements that have been made, followed by the test results of cooling and coil excitations. The four superconducting coils were successfully cooled to less than 4 K and excited accordingly to the designed current densities of 125 A/mm. [ABSTRACT FROM AUTHOR]

The development of new generation, high-performance devices, such as MRI scanners or high-energy accelerators, (may be attributed to the use of) Nb3Sn based superconducting (SC) magnets, which are characterized by their ability to produce much higher magnetic fields than the presently used NbTi-based magnets. Due to the wind-and-react technology of the production of Nb3Sn magnets, new methods and materials for the magnet coil electrical insulation are required. The proper design of SC magnets demands the characterization of thermal properties of the new insulation materials, inter alia, in superfluid helium conditions. This paper provides experimental data of the thermal conductivity and Kapitza resistance for S-glass fiber reinforced ceramic-epoxy (LARP type) electrical insulation, measured in pressurized (at 1 bar pressure) superfluid helium in a temperature range of 1.50-2.00 K. [ABSTRACT FROM AUTHOR]

A subcooled liquid nitrogen cooling system is known as the most promising method for developing a high-voltage superconducting apparatus, such as a superconducting fault current limiter, a superconducting transformer, and so on (Kang et al, IEEE Trans. Appl. Supercond. 18, (2), 628-631 2008). Gaseous nitrogen is injected into a superconducting magnet system to control the pressure and enhance the dielectric characteristics of a subcooled liquid nitrogen cooling system. In this case, the application of a solid insulating barrier between electrodes is regarded as an effective method to enhance the insufficient dielectric characteristics of gaseous nitrogen to develop a transmission superconducting apparatus. Dielectric experiments for a solid insulating barrier made of glass fiber-reinforced plastics (GFRP) in gaseous nitrogen are conducted under various pressures (0.1 ∼ 0.4 MPa), and the results are analyzed. A solid insulating barrier is installed between a rod to plane electrode system. The AC electrical breakdown characteristics according to the pressure of gaseous nitrogen and the position of a barrier between two electrodes are observed. [ABSTRACT FROM AUTHOR]

The linear accelerator, RAON, has been being developed as a part of the Rare Isotope Science Project (RISP) at Institute for Basic Science (IBS) in the Republic of Korea. In this paper, it is dealt with the design of a low T superconducting magnet system for an electron cyclotron resonance (ECR) ion source to utilize a 28-GHz radio frequency source. The superconducting magnet system for a 28-GHz ECR ion source consists of four solenoid coils and six saddle coils (a sextupole coil) (Taylor et al. IEEE Trans. Appl. Supercond. 10, 224-227, 2000). The detail specifications of each superconducting coil are designed by analyzing magnetic field to enhance the efficiency of beam extraction and electromagnetic force to improve the mechanical stability of a superconducting coil by using finite elements method (FEM) simulation. The definitive design parameters for manufacturing the superconducting magnet system for a 28-GHz ECR ion source of RAON accelerator are suggested considering electromagnetic characteristics. [ABSTRACT FROM AUTHOR]

A conduction-cooled superconducting split magnet system with large crossing warm bore has been successfully constructed in our laboratory for material processing applications. The magnet system design was described in a previous paper. The magnet is composed of six NbTi low temperature superconducting coils, which generate 5.5-T central magnetic field and two Bi2223/Ag high temperature superconducting (HTS) insert coils, which generate 2.5-T central magnetic field and assembled in the form of split coil groups. The magnet has a 136-mm split gap to accommodate the crossing warm bore of 100 mm in diameter. The magnet system is cooled by two GM cryocoolers. The initial cooldown takes 9.2 days and the final temperature of the magnet is about 4.0 K. The HTS coils and NbTi coils are to be operated in the driven mode with two independent power supplies, under the operating currents of 200 A (HTS) and 139 A (NbTi), respectively. The magnet is successfully powered up to 8 T with a the ramp time of 290 min. In this paper, the fabrication and test of the superconducting split magnet system are presented. [ABSTRACT FROM PUBLISHER]

A process for developing long-length joint tube assembly of Bi-2223 (10 wt% Ag) superconductor is presented. The process involves sintering of tubes fabricated from cold isostatic pressing of the partially preformed Bi-2223 (10 wt% Ag) superconducting powder. The joint was made between these sintered tubes. For making joints, sintered tubes were physically joined by connecting together on a common superconducting bush coated with a superconducting paste. Subsequently, the combination of the bush and the physically joined portion were sintered. The superconducting properties and phase identification/phase composition of the component tubes and of the joint portions have been investigated. The diametral fractural strength of the component tubes and of the joint portion was also evaluated. In the joint obtained according to this method, it is possible to retain the superconducting properties and the fractural strength of the joint high-temperature superconducting tubes. This technique is very useful for fabrication of very large sized superconducting apparatuses such as external magnetic shielding, transmission cables and electrical current leads, etc. [ABSTRACT FROM PUBLISHER]

High magnetic field magnets are used widely in the area of the condensed matter physics, material science, chemistry, geochemistry, and biology at the National High Magnetic Field Laboratory. New high field magnets of state-of-the-art are being pursued and developed at the lab, such as the current developing 32 T, 32mm bore fully superconducting magnet. Liquid Helium (LHe) is used as the coolant for superconducting magnets or samples tested in a high magnetic field. When the magnetic field reaches a relatively high value the boil-off helium gas bubble generated by heat losses in the cryostat can be trapped in the LHe bath in the region where BzdBz/dz is less than negative 2100 T²/m, instead of floating up to the top of LHe. Then the magnet or sample in the trapped bubble region may lose efficient cooling. In the development of the 32 T magnet, a prototype Yttrium Barium Copper Oxide coil of 6 double pancakes with an inner diameter of 40mm and an outer diameter of 140mm was fabricated and tested in a resistive magnet providing a background field of 15 T. The trapped gas bubble was observed in the tests when the prototype coil was ramped up to 7.5 T at a current of 200 A. This letter reports the test results on the trapped gas bubble and the comparison with the analytical results which shows they are in a good agreement. [ABSTRACT FROM AUTHOR]

We performed systematic current-voltage measurements ( I- V curves) in Ag-added the polycrystalline YBaCuO sample (YBCO/Ag) as a function of the transport current ( I), temperature ( T), external magnetic field ( H), and sweeping rates (d I/d t). Standard and reverse procedures were used in the measurements of I- V curves. The obtained results were compared to I- V curves of the YBCO and polycrystalline sample of MgB. Upon cycling transport current, the I- V curves of the YBCO/Ag sample exhibit hysteresis effects for both procedures and are sensitive to the variation of d I/d t. The experimental data reveal that the irreversibilities in the I- V curves of YBCO are more prominent than those of YBCO/Ag. Furthermore, there are no considerable hysteresis effects in the I- V curve of MgB and this behavior is attributed to the absence of the weak-link structure in MgB. We suggest that the physical origin of the rather small hysteresis effects in the I- V curves of the YBCO/Ag sample can be related to the destruction of weak-link structure due to the addition of Ag into the superconducting matrix. Ag destroys partly the intergranular pinning properties of the YBCO ceramic by increasing grain coupling and, therefore, the irreversibilities in the I- V curves of the YBCO/Ag decrease considerably. The instabilities and short- and long-lived plateau regions observed in I- V curves were explained in terms of plastic flow of flux lines along easy motion channels, which are considered mainly as metallic silver paths in the YBCO/Ag sample. At moderate dissipation levels, we could not observe any difference between the data obtained by using the standard and reverse procedures. This suggests that the surface effects are also weakened by the addition of Ag into the superconducting structure. [ABSTRACT FROM AUTHOR]

In the design of high-temperature superconductor (HTS)-based electromagnetic devices, some of the major challenges include ac loss reduction, minimization of heat leakage, and reduction of the amount of HTS material used to decrease costs. This paper considers a computer model of HTS-based leads involving a multiphysics scenario that considers the electromagnetic and thermal behavior of the system. This paper attempts to address the requirements mentioned and provides an optimum solution by applying an approach based on multiobjective optimization. The differential evolution technique, a stochastic method, widely known for the ease of use and its ability to handle adequately non-differentiable, non-linear, and multimodal cost functions was used. The proposed framework provides a technique to optimize effectively HTS leads, which not only deals with the non-linear aspect of HTS materials, but also includes a multiphysics environment. [ABSTRACT FROM AUTHOR]

The notion of spontaneous formation of an inhomogeneous superconducting state is at the heart of most theories attempting to understand the superconducting state in the presence of strong disorder. Using scanning tunneling spectroscopy and high resolution scanning transmission electron microscopy, we experimentally demonstrate that under the competing effects of strong homogeneous disorder and superconducting correlations, the superconducting state of a conventional superconductor, NbN, spontaneously segregates into domains. Tracking these domains as a function of temperature we observe that the superconducting domains persist across the bulk superconducting transition, Tc , and disappear close to the pseudogap temperature, T", where signatures of superconducting correlations disappear from the tunneling spectrum and the superfluid response of the system. [ABSTRACT FROM AUTHOR]

The article discusses research into possible applications for carbon nanotubes (CNTs), noting the challenges of producing defect-free and aligned high-strength fibers at an industrial scale. Topics include development of polyvinyl alcohol (PVA)-CNT bundles, the wet spinning technique of CNT production, and the potential for magnesium- and boron-incorporated superconducting CNTs for the construction of a space elevator.

We apply the vortex path model of critical currents to a comprehensive analysis of contemporary data on defect-engineered superconductors, showing that it provides a consistent and detailed interpretation of the experimental data for a diverse range of materials. We address the question of whether electron mass anisotropy plays a role of any consequence in determining the form of this data and conclude that it does not. By abandoning this false interpretation of the data, we are able to make significant progress in understanding the real origin of the observed behavior. In particular, we are able to explain a number of common features in the data including shoulders at intermediate angles, a uniform response over a wide angular range and the greater discrimination between individual defect populations at higher fields.We also correct several misconceptions including the idea that a peak in the angular dependence of the critical current is a necessary signature of strong correlated pinning, and conversely that the existence of such a peak implies the existence of correlated pinning aligned to the particular direction. The consistency of the vortex path model with the principle of maximum entropy is introduced. [ABSTRACT FROM AUTHOR]

The design of superconducting magnets for accelerator and detector components dedicated to the future of high energy physics requires detailed analysis of their mechanical behavior, in particular under magnetic and/or thermal solicitations. Numerical simulation is more and more used to optimize these components and to improve their performances in constrained environments. [ABSTRACT FROM PUBLISHER]

All 21 Procurement Agreements (PAs) related to the ITER superconducting magnet system were signed in March 2011. Six Domestic Agencies (DAs) of the seven, namely China, EU, Japan, Russia, the United States and Korea have to deliver components of the magnet system like TF coils and Feeders. In order to organize the complicated international supply-chain, the ITER Manufacturing Database (MD) has been developed as a sub-project of the ITER Engineering Database (EDB) which aims to become the official Product Lifecycle Management (PLM) system of the ITER project. The first version of the PLM was released in August 2011. One of the advantages of the MD is to provide clear definitions of the work conditions and resultant deliverables to all stakeholders for a common understanding and better mutual communication. The work conditions (e.g. applicable code/standard) are basically agreed by all stakeholders after the preparation phase. They are then prepared in the MD as four customized User I/F (interface) screens: the interactive Parts List, the Manufacturing Inspection Plan (MIP), the Welding Quality Inspection and Production Plan (WQIPP) and the Tooling List. Users only upload the required reports (e.g. the mill certificate for each part, test reports) into the corresponding User I/F. Consequently, the filled up User I/F becomes a deliverable, the Manufacturing Dossier. [ABSTRACT FROM PUBLISHER]

The design and fabrication of a 32 T, 32 mm cold bore superconducting magnet with high field REBCO inner coils is underway at the NHMFL. In support of the design, conductor characterization measurements have been made including critical current as a function of field, field orientation, temperature, and strain on conductors and joints. Various conductor and turn insulation systems were examined. The selected coil fabrication method for the 32 T magnet is pancake wind, dry wind coils with sol-gel insulation on a stainless steel co-wind. Quench protection of the REBCO coils by distributed heaters is under development. Small REBCO coils have been made and tested in a 20 T background field to demonstrate performance of the technology. The design of the 32 T magnet is described, including coil configuration and conductor lengths, fraction of critical current, selection of conductor copper content for protection, and stress in the windings. [ABSTRACT FROM PUBLISHER]

A conceptual design of curved superconducting magnet for a carbon therapy gantry has been proposed. The design can reduce the gantry's size and weight and make it more comparable with gantries used for proton therapy. In this paper we report on a combined function, 5 T, superconducting dipole magnet with a 260 mm bore diameter that is curved 90 degrees at a radius of 1269 mm. The magnet superimposes two layers of oppositely wound and skewed solenoids like windings, energized in a way that nulls the solenoid field and doubles the dipole field component. Furthermore, the combined architecture of the windings can create a selection of field terms that are off the near-pure dipole field. Combined harmonics such as a quadrupole and sextupole are needed to adjust the beam trajectory. Ways to adjust the field and beam trajectory, magnet size and assembly, structure and pre-stress are considered. [ABSTRACT FROM PUBLISHER]

We are developing a high-Tc superconducting vector magnet for use in solid-state physics apparatus. The vector magnet features are (a) 1 T peak and two-dimensional magnetic field vector controllable (b) comprising four split magnet units enabling free access in three directions to a sample space (c) cryogen-free conduction-cooled magnet. To obtain a vector controllable magnetic field as high as 1 T using a compact magnet, we adopted a tapered design for split magnet units. We fabricated a test magnet unit with YBCO tape conductors and examined its basic performance. The magnet unit generated the rated magnetic field. This paper describes the vector magnet design, fabrication procedures, and the magnet unit test results. [ABSTRACT FROM PUBLISHER]

The new AEGIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) Experiment will be installed in the Antiproton Decelerator hall at CERN. The main goal is to measure the Earth's gravitational acceleration of antihydrogen atoms. The experiment consists of two high-homogeneity solenoids placed on the same axis. The 5 T magnet is part of a cylindrical Penning trap to catch and to accumulate antiprotons delivered by the decelerator. The antihydrogen is then produced in the 1 T region where sub-kelvin antiproton temperatures provided by the dilution refrigerator are required to form a slowly-moving beam of antihydrogen. The helium bath cooled superconducting magnets; the different traps and the dilution refrigerator are integrated in a common cryostat with an internal vacuum barrier between the insulating cryogenic vacuum and the very high beam vacuum. In addition, the magnet system has to guarantee a smooth transition between the 5 T and the 1 T magnetic field areas required for a loss-free transfer of antiprotons and positrons from the trapping region to the antihydrogen production area. In this paper the design of this AEGIS magnet system is presented and discussed. [ABSTRACT FROM AUTHOR]

An eight-pole superconducting magnet is being developed for soft x-ray magnetic dichroism (XMD) experiments at the Advanced Light Source, Lawrence Berkley National Laboratory (LBNL). Eight conical Nb3Sn coils with Holmium poles are arranged in octahedral symmetry to form four dipole pairs that provide magnetic fields of up to 5 T in any direction relative to the incoming x-ray beam. The dimensions of the magnet yoke as well as pole taper, diameter, and length were optimized for maximum peak field in the magnet center using the software package TOSCA. The structural analysis of the magnet is performed using ANSYS with the coil properties derived using a numerical homogenization scheme. It is found that the use of orthotropic material properties for the coil has an important influence in the design of the magnet. [ABSTRACT FROM AUTHOR]

Superconducting cables for power transmission usually contain two conductors for DC application, or three conductors for AC, with high voltage insulation. In contrast, for some applications related to accelerators it is convenient to transfer high currents via superconducting links feeding a number of circuits at relatively low voltage, of the order of a kilovolt, over distances of up to a few hundred meters. For power transmission applications based on cooling via sub-cooled liquid nitrogen, suitable HTS conductors are only available in the form of tape, and a multi-layer variant can be envisaged for the multi-circuit links. However, where cooling to temperatures of the order of 20 K is feasible, MgB2 conductor, available in the form of both tape and wire, can also be envisaged and in the latter case used to assemble round cables. There are, therefore, two distinct topologies—based on the use of wires or tapes—that can be envisaged for use in applications to multi-circuit link systems. In this paper the merits of the two approaches are compared, and case studies related to applications to the LHC are presented. [ABSTRACT FROM AUTHOR]

This paper investigates subharmonic resonance, one of typical nonlinear phenomena, appearing in a high-Tc superconducting bearing system. In such low-damping systems having noncontact support by magnetic force, complex dynamical behaviors can be caused by nonlinearity of the magnetic force. In this study, the magnetic rotor, supported by a high-Tc superconducting bulk, is bound to a D.C. motor with a universal joint. According to the equation of motion, caused by the quadratic term of the levitation force, subharmonic resonance of the rotor can occur when the rotor rotates, not at its critical speed, but at twice its critical speed. This analytical prediction was confirmed by our numerical and experimental results. Additionally, our study also found occurrence of internal resonance induced by this subharmonic resonance. These findings beyond linear regimes can be important for the design of high-Tc superconducting levitation systems. [ABSTRACT FROM AUTHOR]