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This paper presents a review of studies of superconductors with a porosity above 50%. The pores in such superconducting materials allow refrigerant penetration and provide efficient heat dissipation and stable operation. Methods for the synthesis of the main groups of porous superconductors are described. The results of studies of the structural, magnetic, and electrical transport properties are presented, and the features of the current flow through porous superconductors of various types are considered. The directions of further development and application of porous superconductors are presented. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the thermal runaway characteristics of a conduction-cooled Bi2212 HTS coil with a 4 K-GM cryocooler system under compensating operation for load fluctuations. We measured the temporal evolutions of temperature and voltage distributions of the HTS solenoidal coil for typical current patterns of load fluctuation compensation at different ambient temperatures. On the basis of these experimental results, we constructed a thermal analysis model, and analysed the thermal runaway characteristics during and after the load fluctuation compensation. Based on the results of our experiments and the numerical simulations, we proposed criterion for the monitoring of an HTS SMES system during compensating operation for load fluctuations. [ABSTRACT FROM AUTHOR]

Development of the SMES using high temperature superconducting (HTS) coil has progressed as a Japanese national project since FY 2004. The objective of the project is to obtain around twice the normal energy density via an HTS-LTS ‘hybrid’ coil system compared to an LTS coil system. The HTS coil is composed of sixteen double-pancake coils and the double-pancake coil is wound with a Bi2212 Rutherford-type cable. The HTS coil is operated at 4.2 K in liquid helium bath with the LTS coil, and operated at maximum field of 8.9 T. Before we made a hybrid coil system, we verified the design issues using HTS experimental coils. In this paper mechanical compression tests, DC operation tests and thermal runaway tests using the experimental coils are discussed. [ABSTRACT FROM AUTHOR]

The CFETR, “China Fusion Engineering Test Reactor,” is a new tokamak device. Its magnet system includes the toroidal field (TF), central solenoid (CS), and poloidal field coils. The main goal of this study is to build a fusion engineering tokamak reactor with fusion power of 50–200 MW and self-sufficiency by blanket. The maximum field of CS and TF will get around 15 T, which is much higher than that of other reactors. New materials could be used to develop the magnet technology for the next generation of fusion reactors. Bi2Sr2CaCu2Ox is considered as a potential material for the superconducting magnets. An R&D activity is running at ASIPP for the feasibility demonstration of cable-in-conduit conductor based on the Bi2212 wire. One subsize conductor cabled with 42 wires was designed and manufactured. In this paper, the manufacturing procedures and first test results of Bi-2212 conductor samples are described in details, including wire specifications, cabling and compaction process, conductor heat treatment, as well as test results on ac loss and critical current. [ABSTRACT FROM PUBLISHER]

Practical superconducting materials and technologies have been enabled with availability for large scale devices and applications. Various large scale and strong magnetic field applications of superconductors have been developed, and a series of those applications are explored with technical details mainly including i) applied superconducting materials and their characteristics; ii) superconducting magnets and their techniques; iii) large and advanced electromagnetic devices and applications. The applied superconductivity, application technology, and availability are especially focused and verified with the trend of large scale applications’ development prospection. [ABSTRACT FROM AUTHOR]

The U.S. Magnet Development Program (US-MDP) is aimed at developing high-field accelerator magnets with magnetic fields beyond the limits of Nb3Sn technology. Recent progress with composite wires and Rutherford cables based on the first generation high-temperature superconductor Bi2Sr2CaCu2O8−x (Bi2212) allows considering them for this purpose. However, Bi2212 wires and cables are sensitive to transverse stresses and strains, which are large in high-field accelerator magnets. This requires magnet designs with stress management concepts to control azimuthal and radial strains in the coil windings and prevent the degradation of the current carrying capability of Bi2212 conductor or even its permanent damage. This paper describes a novel stress management approach, which was developed at Fermilab for high-field large-aperture Nb3Sn accelerator magnets, and is now being applied to high-field dipole inserts based on Bi2212 Rutherford cables. The insert conceptual design and main parameters, including the superconducting wire and cable, as well as the coil stress management structure, key technological steps and approaches, test configurations and their target parameters, are presented and discussed.

The microstructure and superconducting properties of Bi-2212 wires seem to be strongly influenced by the nominal composition of the starting powder. We fabricated Bi-2212 round wires with different starting compositions. The highest Jc values of 175 kA/cm^2 at 4.2 K and 10 T were obtained in the Bi-rich sample with a Bi-rich composition. We carried out quenching experiments from the melting state of Bi-2212. We observed obviously smaller grains of impurity phases in the wire with high Jc than in the low-Jc wires in the melting state, which suggested that this is one of the reasons for the enhancement of the Jc values in these wires. [ABSTRACT FROM AUTHOR]

Zirconium oxide inclusion in Bi2212 superconducting tapes and bulks was studied as possible artificial pinning centers (APC). In order to analyze the zirconium oxide APC addition in Bi2212 samples, magnetization measurements were performed in bulks and transport properties measurements were performed on tapes. In magnetization measurements, the critical current densities are proportional to the width of the magnetization loop at each applied magnetic field. Addition of ZrO2 in Bi2212 superconductors broadened the magnetization loop and enhanced the critical current densities at 4.2 K in bulks, as a clear indication that ZrO2 addition improved the pinning and acted as APCs. In contrast, the transport critical current densities decreased in tapes. [ABSTRACT FROM AUTHOR]

A new approach to magnet fabrication, react, wind and sinter (RWS), has been proposed for Bi2Sr2CaCu2Ox (Bi2212), magnets. In this process, the conventional Bi2212 heat treatment is split into two portions, and the magnet is wound between these heat treatments. Here we report results on the RWS "split melt process". Significant increases in Ic are obtained in Bi2212 round wires compared to standard melt processing. Strain effect measurements, using the Lorentz force, indicate that RWS wires have similar mechanical performance as wind and react wires. Effects of the split melt temperature on the electromechanical properties are also reported. These results show that split melt processing and RWS magnet fabrication are viable approaches for Bi2212 conductors and magnets. [ABSTRACT FROM AUTHOR]

High-Tc superconducting technology is thought to provide many merits for SMES systems. For example, a cryocooled system can be used as a cooling system for High-Tc superconducting coils, indicating that an operation temperature can be selected from a wide-temperature range below critical temperatures. Refrigerator cooling operation temperature for High-Tc SMES can be elevated more than 20 K from conventional 4.2 K. As a result, the heat capacity of coil system becomes much larger than that at 4.2 K, indicating that thermal diffusion time constant becomes much longer. If we could absorb transient heat generation with heat capacity of the coil, SMES systems can be designed under the over current state of critical current for a short duration. As a cooling capacity for an average heat load will be enough to cool High-Tc superconducting coil system for SMES, the refrigerator system cost can be much lower than that for a SMES system using Low-Tc superconductors. Moreover, we are developing high critical current superconducting wire for SMES system. The Bi2212 Rutherford conductors can carry 4 kA at 26 K under cryocooling. We also estimate the superconducting wire cost of the whole coil system, which is designed to minimize the superconductor volume. The conclusion is that the cost of High-Tc SMIES system will be reduced by using the low-cost YBCO superconducting wires in the future. [ABSTRACT FROM AUTHOR]