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The various effects of temperature on the Ginzburg-Landau parameter, thermodynamic and upper critical field of the [Nb.sub.3]Sn strands are being discussed. The results show that the surface barrier is responsible for the asymmetry shown in the magnetic relaxation rate for flux entry and exit.

The Heating surge and temperature oscillation is analyzed in the poloidal field (PF) and toroidal field (TF) coils of Korean Superconducting Tokamak Advanced Research (KSTAR). The experimental results show that the maximum temperatures in TF and PF are about 5.7 K and 5.9 K respectively.

The Korean Superconducting Tokamak Advanced Research (KSTAR) device is a tokamak with a fully superconducting magnet system, which enables an advanced quasisteady-state operation. The effect of three-dimensional heat conduction and the eddy current loss in the vacuum chamber of KSTAR is described.

The relationship between the current density and magnetic flux density is studied by using Turner's target field approach for spherical conductors. The results show that by using this method, uniform or gradient magnetic field that vary linearly along the x or y direction can be generated.

Properties of ferromagnetic materials are measured at liquid nitrogen temperature.

The effects of transformer geometry on magnetic field leakage are examined and reported.

Research involving simulations of dynamic stress in PF (Polodial Field) superconducting magnets for the KSTAR ( Korea Superconducting Tokamak Advanced Reactor) is described and discussed.

A relation between travel of the bending roller and spring back radius is described. The relation was obtained by means of virtual manufacturing with a 3-roll bending process.

MFEM1D, a numerical method based on the finite-element method, is described. It is used to investigate the helium expansion and quench propagation in cable-in-conduit conductors (CICC).

Effects of inlet pressure and mass flow rate on the temperature margin and heat-removal characteristics of the Samsung Superconducting Test Facility (SSTF) are examined and discussed.

Thermal analysis of the Korea Superconducting Tokamak Advanced Research (KSTAR) device's poloidal field (PF) was accomplished using the code SAITOKPF

The development of conductors with an aluminum super-stabilizer was proposed for some applications of accelerator detector magnets for high-energy physics and superconducting magnet storage energy devices. The conductors are designed with the cryogenics stabilization by using a large amount of low resistance aluminum stabilizer. However, it has induced to some new problems. One of these is the effect of the current redistribution between superconducting strands and stabilizer on the quench propagation and stability. In this study, we assume a superconducting magnet to be immersed in liquid helium. A quasi-three-dimensional model is proposed to study thermal diffusion in superconducting magnet and current diffusion is based on the solution of Maxwell's equation. The uniform temperature distribution in the cross-sectional area of conductor is taken into account due to the high thermal conduction of stabilizer and small size compared with the length. An adaptive mesh scheme COLSYS is employed to capture the solution of temperature and current in the front of normal position. The computational model includes nonlinear thermal and electrical characteristics in superconducting strands and aluminum stabilizer and heat transfer of helium. The influence of current re-distribution between stabilizer and superconducting strands on the quench is studied. Index Terms--Adaptive mesh, current diffusion, normal zone of finite length propagation, quasi-three-dimensional numerical model, quench, stability, superconducting magnet.

The background magnet system on the Samsung Superconductor Test Facility for Korea Superconducting Tokamak Advanced Research is discussed.

Research describing the quench characteristics of a superconducting magnet consisting of several pancake shaped coils is presented. The application of the moving mesh finite volume method to a simulated quasi-three-dimensional model for quench processes is investigated.

Research is presented describing the design of a 50 kA superconducting transformer that charges a cable-in-conduit conductor (CICC) short sample for one sescond. The transformer is part of the Samsung Superconductor Test Facility, that is being designed for Korea Superconducting Tokamak Advanced Research.

The stability margin of NB3Sn cable-in-conduit-conductor was assessed using a numerical model, based on the finite volume technique.

The transition temperature T(sub c), the thermodynamic critical field B(sub c), and the upper critical fields B(sub c2) of Nb(sub 3)Sn were numerically calculated by Eliashberg theory of strongly coupled superconductors using the Einstein spectrum. It was found that the impurity concentration was relatively low and the strain effects were due to the phonon mode softening both at high and low frequencies.

As a part of a conceptual design study for a steady-state demonstration reactor (K-DEMO) of which the major and minor radii are around 6.5 and 2.0 m, respectively, toroidal field magnets which can generate around 8 T at plasma center with a peak magnetic field of \sim16 T are being studied. For conductor tests under such a high magnetic field, a new conductor test facility is required and a conceptual design activity is going on, in parallel. The conductor test facility, named SUCCEX (SUperConducting Conductor EXperiment), will feed the sample with a current up to 100 kA and the sample temperature will be varied from 4.5 K to \sim20 K. Moreover, Sultan-like conductor tests, U-shaped joint-less sample tests will be conducted. The 16-T \Nb3 \Sn magnet, with a bore of \sim1-m diameter, is divided into three concentric split pairs, inner coil (IC, peak field of 16.4 T), middle coil (MC, 13.6 T), and outer coil (OC, 7.9 T), connected in a series, with a nominal operating current of \sim18 kA. Each split pair coil is made of its own distinctive rectangular shaped cable-in-conduit conductor (CICC). The overall design concept and preliminary results of electro-magnetic, structural, and thermo-hydraulic analysis are presented. [ABSTRACT FROM PUBLISHER]

Two identical conductor samples were fabricated from 110 m length cable prepared for qualification of the manufacturing process for Phase II procurement of ITER TF conductor. Superconducting strand characteristics, cabling specifications, and the stainless steel jacket sections are described. Sample assembly and instrumentation of various voltage taps and temperature sensors have been prepared according to specified procedures for conductor performance qualification. The performance test program which was agreed to by the SULTAN working group was applied to the conductor samples. To assess the current sharing temperature (Tcs), standard analysis procedures were adopted. The Tcs of both samples at 68 kA with a background field of 10.78 T after a 1000 cyclic load are well above the acceptance criteria. Behavior of individual “star” voltage taps which are located at different positions and which are possible origins of rather large discrepancies in the Tcs of identical samples is discussed. The effective strain and the transition index of the samples are obtained from the experimental data. [ABSTRACT FROM PUBLISHER]

While the manufacturing of superconducting CICC (cable in conduit conductor) and winding conductors into winding packs for ITER TF magnets, cold work is unavoidably applied on the jacketing tube. This article investigates the effect of plastic deformation on low temperature mechanical and magnetic properties of austenite 316LN stainless steel tube for ITER TF conductor. To simulate the manufacturing process of TF magnet, tubes were compacted, extended to 2.5% in longitudinal direction and heat treated. After each step, specimens were sectioned using wire cutting EDM, and tensile tests at 4 K, magnetic susceptibility measurements, and hardness tests have been carried out on those specimens. Remarkable reductions of elongation at failure have been observed as the amount of cold work is increased through compaction and extension. Further, correlations among results of tensile tests, magnetic susceptibility measurements and hardness tests are presented. [ABSTRACT FROM PUBLISHER]

An optimization design method of short-length actively shielded and open structure, superconducting MRI magnets is suggested in the paper. Firstly, the section of the solenoid coil is simplified as a current loop with zero section to solve a linear programming problem. The position coordinates in the radius and axial, and current for the loop can be calculated by the linear programming method. Then, the cross-section of the coil is optimized with a genetic algorithm to get appropriate section size. The method of linear programming, especially combining with genetic algorithm, reduces optimizing variables, which makes the design of a magnet feasible. Based on the method, a full open MRI superconducting magnet is designed with maximum radii of 0.8 m and 1.2 m. In the paper, the detailed optimization technologies are presented. [ABSTRACT FROM AUTHOR]

There are a lot of experimental reports on the scaling of flux pinning in the form of F : Fmbl/2(1 - b)2, with b = B/Bc2. The temperature dependence of Fm is approximately proportional to B[(Multiple line equation(s) cannot be represented in ASCII text)], whereas the strain dependence of Fm is reported to be proportional to the upper critical field Bc2. In this work, we re-analyze our previous data with the Kramer model including the pin-breaking dynamic pinning force (Fp) for a low field region. It is shown that the extrapolated upper critical field B*c2, strongly depend on the ratio between the mean of the parameter Kp for Fp (< Kp >) and the parameter Ks for the flux line lattice shearing pinning force Fs. It is found that the strain dependence of Fm at 4.2 K is approximately proportional to (B*c2) 1.5. We further compare the data with the prediction of our recent scaling theory based on Eliashberg theory of strongly coupled superconductors. It is shown that the strain dependence of Fm at 4.2 K is proportional to B[(Multiple line equation(s) cannot be represented in ASCII text)] κ-2, consistent with the temperature dependence of Fro. Moreover, this model agrees reasonably well even with the data in a high compressive strain region (<-0.8%). [ABSTRACT FROM AUTHOR]

We report detailed magnetization measurement results for two internal-tin Nb3Sn strands. The paramagnetic background of a Mitsubishi strand is about 4 times larger than that of a KAT strand below the transition temperature, which can be understood as combined effects of Pauli and Langevin paramagnetism. From magnetic relaxation measurement for the KAT strand, a possibility of surface barrier effect is discussed. After subtracting the paramagnetic background, reversible magnetization data are analysed using the Hao-Clem model and the Ginzburg-Landau parameters (κ), the thermodynamic and the upper critical fields (Bc, Bc2) at various temperatures are obtained. The temperature dependences of κ, Bc and Bc2 are compared with the recent theoretical calculation results for Nb3Sn and also with widely used empirical formulas. [ABSTRACT FROM AUTHOR]

The development of a high performance superconducting magnet requires a thorough understanding of the strain effect in the critical current density (Jc) of Nb3Sn strands. A modified version of the WASP device is used for the investigation of the strain effect. The spring is made of BeCu alloy and is capable of applying strain up to 0.7% reversibly at 4.2 K. Several types of high performance Nb3 Sn strands (Jc > 1000 A/mm² at 12 T and 4.2 K) have been developed using internal tin process. A comparative study on the axial strain dependence of the critical current is performed. [ABSTRACT FROM AUTHOR]

The Korea superconducting Tokamak Advanced Research (KSTAR) device, a steady-state-capable advanced Tokamak, is to be built in Korea. The KSTAR device is made up of 16 toroidal field (TF) and 14 poloidal field (PF) superconducting coils. A simulation code for the transient operation of the KS TAR TF and PF coils is developed. For stable Tokamak operation, the operating characteristics of the KSTAR superconducting magnet system are studied for operation scenario. We calculated the temperature margin of superconducting cables, cryogenic flow parameters and the heat deposition in TF and PF coils. The effect of the three-dimensional heat conduction and the eddy current loss in the supporting structure and vacuum chamber of KSTAR is also included. [ABSTRACT FROM AUTHOR]

The properties of the magnetic materials, such as the amorphous alloys and the grain-oriented silicon steels, are essential to the design of high-temperature superconducting transformers. In this paper the magnetic properties and the loss characteristics of different ferromagnetic materials are measured at liquid nitrogen temperature. It is shown from experimental results that at 77 K the saturation flux density of the amorphous metal is about 0.3 T lower than that of the silicon steel, and the loss of amorphous metal is 4 times less than that of the silicon steel. Since the losses of materials at 77 K are higher than those of at room temperature, it is not economical to immerse the transformer core in liquid nitrogen. [ABSTRACT FROM AUTHOR]

The leakage magnetic field in HTS transformer windings fabricated by Bi-2223 tapes decreases the critical current and increases the ac losses in the tapes. Because of the anisotropy of the HTS tape, the numerical analysis of the radial component of the leakage field is especially important. In this paper the influence of the core structure and the winding configuration on the stray field is studied by finite element method, and some suggestions for improving the leakage field distribution are presented to make HTS transformers more efficient. [ABSTRACT FROM AUTHOR]

Abstract: A comparative study on the effects of heat treatment, especially, the duration of the A15 reaction temperature plateau on the strain dependence of the critical current for an internal-tin processed Nb3Sn strand has been carried out. The strain dependence of the critical current is measured by a variable temperature Walter spiral probe that we have developed. It was shown that prolonged heat treatment can be a very effective way to improve the strain dependency. For a quantitative analysis, the measured data were analyzed with various proposed scaling laws: the scaling law based on strong-coupling theory, the modified deviatoric strain scaling law, and the interpolative scaling law. We found that there is a slight increase in the critical temperature and a substantial improvement in the maximum pinning force. The origin of improved strain dependency is further discussed. [Copyright &y& Elsevier]