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Investigating the verified E-J characteristics of Bi-2223/Ag tapes in a low temperature and high field having two directions predicted by the percolation model, using limited data measurements is presented. This method makes it possible to understand the properties of HTS for wide T and B ranges and to optimize the design for applications.

Having investigating the extended E-J characteristics in an YBCO coated IBAD tapes are presented. It is concluded that the LTSLM is a powerful tool to study the local superconducting properties in YBCO coated tapes.

High temperature superconducting current feeders were developed for a large-scale superconducting experimental fusion system.

Superconductors were studied under fast current change to determine quench development and ultimate normal zone propagation velocity.

The magnetic phase diagram was constructed in small-volume high temperature superconductors using an open-flat coil magnetometer.

Research describing thermal quench in high temperature superconducting magnets is presented. The theory of universal scaling is used for the analysis of thermal quench emergence conditions.

The Large Helical Device helical conductor was studied and temperature and electric field distribution measurements taken.

A study of the possible solutions to the problem of 'single strand stability' in multistrand superconducting cables is presented. A proposed change in the design of the cable, aimed at improving its stability in relation to the quench of a single strand, is evaluated. This is accomplished by testing a number of multistrand superconducting cables manufactured from insulated superconducting strands that utilizes varying cabling techniques.

A study of quench propagation in double-sided samples of high temperature superconducting YBaCuO thin film that were covered by a gold top layer has been conducted. The large-area YBCO films, which were deposited on sapphire wafers, exhibited complicated processes of quench development. The results suggest a strong effect of thermal interaction on quench development between the two films in double-sided samples due to the substrate's heat conductivity.

A study of the quench dynamics of an YBaCuO high temperature superconductor (HTSC) film and a bismuth-based small HTSC coil is presented. The nonlinear resistance in HTSC, a function of transport current and temperature, emerged as the crucial parameter for the quench. The results indicate that the dynamic attributes of the quench in both the coil and the film can be quantitatively defined by the simplified one-dimensional heat balance equation.

A 1kWh/1MW module-type semiconducting magnet energy storage (SMES) called Experimental SMES of Kyushu Electric Power Company Inc has been developed. The main points of its design are the converter-coil module system, modified-D shaped coil with mechanical support, newly developed high temperature superconducting current leads, total system operation and liquid helium-vessel type cooling. Results of preliminary test indicate the expected control function of the SMES system in the extent of its capacity.

The development of the current bus line with conductor-holder for the melt textured YBa2Cu3O(sub x) bulk conductor is described. The objective was to moderate Joule heat generation in high current transport experiments at 4.2 K. Experimental results illustrate the feasibility of the application of the melt textured YBa2Cu3O(sub x) bulk conductor to the current feed device for the Large Helical Device.

A design study for the fabrication of a module-type Superconducting Magnetic Energy Storage system with a 1 kWh maximum stored energy and 1 MW maximum power capability was conducted. Design considerations include module-type coils consisting of three coils and a converter, low loss stranded cables, modified D shape coils and high temperature superconducting current leads. The system is scheduled for installation in a power system after completion in 1997 and 1998.

A 500 kVa-class oxide superconducting transformer for subcooled nitrogen operations was designed, constructed and tested. Three- and six-strand parallel conductors of Bi-2223 silver-sheathed multifilamentary tapes acted as the primary and secondary windings, respectively. The transformer was then installed in a continuous flow subcooled nitrogen system. It was operated up to critical current levels of 66 K without quenching.

A theoretical study was conducted on the alternating current losses in superconducting parallel conductors consisting of Bi2223 multifilamentary wires for power transformer windings. An analytical expression was developed for the additional coupling loss. The current distribution in solenoidal coil strands of the parallel conductor was also calculated experimentally and the influence of transposition on current distribution was examined.

The Monte Carlo method was employed in analyzing the flux dynamics in a random pin medium. Results show that the disordered system exhibits percolative flux depinning with stochastic property reflected by the scaling of electric field vs current density curves. The analytical expressions for magnetic field and temperature dependent curves were quantitatively consistent with measurements in Y1Ba2Cu3O7-delta thin film at different magnetic fields and temperatures.

The paper describes the test results of a 100A persistent current switch and the design of a 1.5kA persistent current switch. These switches are of transformer-type, based on the principle of a current transformer. In order to increase resistance in the switch-off mode, bifiliar windings with negligible small inductance are inserted into the secondary circuit of the transformer. The test of the 100A persistent current switch has been performed with satisfactory results such as the switch-off resistance of 50 [ohms], the switch-off time delay of 20 ms and the operational current of 100A. The 1.5kA persistent current switch has been also designed to have a shorter response time than 100ms and a switch-off resistance larger than 100 [ohms].

The Large Helical Device (LHD) under construction at NIFS is a nuclear fusion experimental device consisting of two superconducting helical coils and three pairs of poloidal coils. A pair of inner vertical (IV) coils with a combined stored energy of 161 MJ have been delivered to NIFS. They were the 4 m outside diameter coils wound from cable-in-conduit conductors composed of 486 strands with a copper matrix. We conducted supercritical helium cooling and excitation tests to confirm the cooling and superconducting characteristics of one of the IV coils before its assembly into the LHD cryostat in 1997. It has been assembled into the SHe test facility at the Toki site of NIFS, and was cooled down and energized to 2.2 kA in February and March 1995. The test facility will be repaired in part, and the coil will be tested to confirm the characteristics at the rated current of 20.8 kA within the year.

The flux creep properties of c-axis oriented YBa2Cu3O(7-delta) thin films were extracted from frequency-dependent voltage-current curves obtained via four-probe measurements. Specifically, the maximum creep field at which flux creep shifts to become flux flow was derived along with the pinning distribution. From these, the electric field of the flux creep was calculated and it was concluded that the flux flow causes low-temperature dissipation.

The ac losses induced by periodic longitudinal fields in superconducting wires were studied. Specifically, ac loss measurements of short samples of multifilamentary niobium titanium wires subjected to an oblique external field were carried out at one hertz and 60 Hz. The measurements were repeated on triple-twisted superconducting cables. Both experiments demonstrated that ac losses at 60 Hz are equivalent to the sum of hysteresis loss and coupling-current losses due to the transverse component and longitudinal component of the external fields, respectively.

The ab-plane magnetic penetration depth in c-axis-oriented YBaCuO thin films was studied. The resonance method was used in forecasting the magnetic penetration depth based on inductance measurements. It was shown that the temperature dependence of the films was compatible with the local limit calculation of the thin films, which was based on the theoretical assumptions of the Bardeen-Cooper-Schrieffer theory. It was also concluded that the bias current had affected the magnetic penetration depth of the thin films.

Work on the Large Helical Device (LHD) currently being built at Japan's National Institute for Fusion Science is reported. A nuclear fusion structure, the LHD consists of superconducting magnets which are configured as helical coils, poloidal coils and vertical coils. The various coils are described along with the cryostat and cryogenic supports. Ongoing work include the design of additional poloidal coils.

Atheoretical study of additional ac losses in the armature winding of a superconducting generator is presented. The analysis, which concerns multiply-layered cables composed of multifilamentary superconductors, was conducted under conditions of an applied ac transport current and ac transverse magnetic field. To lower the total ac loss, issues related to the optimization of the winding's cable structures are also presented.