[en] The authors have succeeded in constructing a novel face-to-face field generator using seven RE-Ba-Cu-O bulk superconductors arranged on a couple of wide cold stages with a size of 150 mm in diameter. The cold stages were cooled to 67 K by using Stirling-cycle pulse tube cryocoolers (8 W at 77 K), and magnetized by the field cooling process operated by a superconducting solenoid magnet at 5 T. The highest magnetic field has reached 1.4 T on the pole surface and 0.9 T at the center of the open space of 34 mm between the bulk magnets, respectively. The maximum value of the total fluxes has reached 4.5 mWb that corresponds to nearly four times as much as that obtained when a single bulk sample was magnetized at 35 K. The intense magnetic fields are investigated to be applied to various industries such as magnetic separation systems and so on in Iwate CREATE project

[en] We aim to apply the superconducting bulk magnets to high gradient magnetic separation technique. Two bulk magnets are face-to-face arranged and a pipe stuffed magnetic filters composed of ferromagnetic wires is placed between the magnetic poles. We setup the magnetic separation system and test it using slurry mixed with hematite particles (Fe₂O₃). Y123 bulk superconductors are magnetized by the 'IMRA' method (pulsed-field magnetization), and consequently a magnetic field of 1.59 T is generated at the center of 20 mm gap between the magnetic poles. As a result of experiment on the magnetic separation, hematite particles of over 90% were removed from slurry at the flow rate of 2 l/min

[en] We study on the magnetization behavior of to magnetize RE123 bulk superconductors to apply it as strong magnets. Through magnetizing process, the temperature of bulk superconductors is raised by pinning loss caused by the magnetic fluxes motion (e.g. flux jump of flux flow), and the trapped field is decreased. This paper presents the measurement of temperature changes of Sm123 bulk superconductors during the exciting process by iteratively magnetizing pulsed-field operation with reducing amplitudes (IMRA) method. Five thermocouples are put on the surface of Sm123 bulk superconductor of 46 mm in diameter. The temperatures at the center, on the growth sector boundary (GSB) line and in the sector region surrounded by GSB's line (inter-GSB region) are monitored. The temperature at a cold stage is also measured. A Hall sensor is attached near the center thermocouple to measure the trapped field. After a bulk superconductor is cooled by the GM type refrigerator until 40 K, iterative pulsed-fields of 2.32-5.42 T are applied by a magnetizing coil. When high magnetic field of 5.42 T is applied, a temperature of bulk superconductor reaches to 72.4 K and the magnetic field distribution has C form with which a part of circle is dented, and then, a trapped field is 2.28 T. When a lower magnetic field of 4.64 T is applied, a maximum temperature is 68.3 K and a trapped field is raised to 2.70 T, and moreover, the distribution becomes round shape like field-cooling method (FC). We showed clearly that heat generation by pinning loss was related to the mechanism of magnetic field capture

No abstract available

[en] The formation process of Nb/sub 3/Al by a solid state reaction between Nb and Al is examined for both powder metallurgy processed wires and sputtered multilayer films. It is turned out that the diffusion of Al into Nb layer plays an important role in the formation process of Nb/sub 3/Al, but the extremely thin Nb thickness is not necessarily needed for the solid state reaction on the basis of the study of multilayered films. The authors discuss on the relationship between the Nb layer thickness and the areal reduction ratio to the Nb/sub 3/Al formation in the powder metallurgy process

[en] In the High Field Laboratory for Superconducting Materials at Tohoku University, we have built up in the last four years three hybrid magnets capable of 30 T, HM-1, HM-2, and HM-3. Two of these magnets, HM-3 (32 mm bore, 20 T) and HM-2 (52 mm bore, 23 T) have been already made available for the development of superconducting materials for nuclear fusion reactors. The outer, superconducting, parts SM-3 and SM-2 of these magnets, wound with multifilamentary NbTi conductors, can both generate 8 T and have the room temperature bores of 220 and 360 mm, respectively. The fabrication of HM-1, the maximum field of which had been designed to be either 31 T (32 mm bore) or 29 T (52 mm bore), was finished last spring and we succeeded in generating 30.7 T on May 29, 1985. A 12-T superconducting magnet (SM-1) with a room temperature bore of 360 mm was used in HM-1. SM-1 used Ti-doped Nb₃Sn multifilamentary couductor. The design, construction, test and operation of these three superconducting magnets are reported in detail. A few examples of H /sub c2/ and J /sub c/ measurements in HM-1 are also presented

[en] We have measured the thermal conductivity (κ) of bulk Y-Ba-Cu-O blocks welded with sintered Er-Ba-Cu-O and Y-Ba-Cu-O/Ag at temperatures between 5 and 300 K. For comparison, the thermal conductivity was also measured for melt-textured Y-Ba-Cu-O and Er-Ba-Cu-O. All the samples showed the enhancement of κ at around 50 K, which was commonly observed in high temperature superconductors. The maximum κ values were 90 mW/cm K for both welded Y-Ba-Cu-O and melt-textured Er-Ba-Cu-O and 150 mW/cm K for melt-textured Y-Ba-Cu-O. Such differences have originated from different microstructural features

No abstract available

[en] In order to improve the strain/stress characteristics of the critical current I_c, the use of external CuNb reinforcing stabilizer, instead of the conventional Cu stabilizer, with bronze processed Nb₃Sn multifilamentary superconducting wires was examined up to the magnetic field of 14T and at a temperature of 4.2K. Although the axial tensile strain sensitivity of I_c was not changed, the strain for peak I_c as well as the reversible strain limit increased by 0.14% when the Cu stabilizer was replaced by the CuNb reinforcing stabilizer. On the other hand, the transverse compressive stress sensitivity of I_c decreased and the reversible stress limit increased. An increase in both a bronze to Nb ratio and Sn content in bronze matrix resulted in a higher stress tolerance and, as a consequence, the contribution of the CuNb reinforcement became relatively small

No abstract available