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The effects of thermal neutron irradiation and excess oxygen on the properties of Ti-sheathed MgB2 wires were investigated separately in this paper. No significant influence was observed when thermal neutron irradiation with fluence levels of 1.23 x 1014 and 5.75 x 1014 cm2 were applied on the sample, while fluence level of 3.16 x 1015 cm2 provided a strong suppression of in-field critical current density. Excess oxygen in sample preparation process had negative effect on the properties of the MgB2 wires. The samples prepared in air possessed lower critical temperature and in-field current carrying capability in comparison with the sample prepared in glove box. [ABSTRACT FROM AUTHOR]

Magnesium Diboride has a great potential for magnet applications in many areas such as high energy physics, Mill, and space-related projects. The main goal of our ongoing research effort is to study magnet design, winding process, and magnet testing. Last year, in a 14 cm bore solenoid we reached a central magnetic flux density of 1 tesla at 16K with almost 500 m of commercial multi-filament tape. In order to design appropriate quench detection and protection systems, it is important to define the quench propagation characteristics in solenoids made with this superconductor. In this work we show our experimental activity, from winding to testing, with a 14 cm bore solenoid made with commercial multi-filament MgB2 tape. In particular we address a quench propagation study on a coil made with 2 m of the same tape. [ABSTRACT FROM AUTHOR]

Sharp cube textured Ni-9%atW alloy substrates were successfully achieved using the powder metallurgy process and gave promise for coated conductor with reduced AC losses and improved mechanical properties. X-ray studies indicated that the newly developed Ni-9%atW alloy substrates have a good out-of-plane and in-plane orientation with FWHM values about 3.7° and 7.05° respectively. Smooth surface as well as fine grains were obtained in the newly developed textured substrate. Curie temperature is suppressed to be 30 K and magnetic hysteretic losses are zero for Ni-9%atW alloy substrates at 77 K. [ABSTRACT FROM AUTHOR]

Many efforts have been made to improve the current carrying capability of Y1Ba2Cu3O7 (YBCO) films by introducing pinning centers using a variety of techniques. In this study, we have succeeded in producing Y2O3, BaZrO3 and Sm doped YBCO films for the development of coated conductors by a metal-organic deposition method using trifluoroacetates (TFA-MOD). Jc exceeding 5 MA/cm2 at 77 K and self field was obtained in Y2O3 doped YBCO film. Also it was found that YBCO films with Sm substituting for Y have shown an improved critical current density characteristic over a wide range of magnetic fields. A Jc of 0.25 MA/cm2 at 3 T and 77 K was obtained which is more than 10% of the zero-field Jc. Similar results were obtained in BaZrO3 doped YBCO films. Additionally, TEM analysis was performed to study the microstructures and the pinning mechanisms. The results indicate that significant enhancement of self-field and in-field Jc of Y2O3, BaZrO3 and Sm doped YBCO films may be due to introducing nano-scaled Y203particles, nano-scaled 90° rotated Y1/3Sm2/3Ba2Cu3O7 domains and BaZrO3 nanodots by different chemical doping, respectively. This indicates that chemical doping is a promising approach for enhancement of current carrying capability of YBCO coated conductors. [ABSTRACT FROM AUTHOR]

The properties of MgB2 have the potential to make this material a viable solution for applications in which temperature, costs or weight are considered relevant constraints. In order to realize large scale applications, it is important to investigate the material, but also the winding process for MgB2 wires and tapes. In the literature small coils have already demonstrated central magnetic flux density above 2 Tesla, overcoming common winding problems related to MgB2 wires. In this current research, efforts are being made in order to improve the performance of solenoid coils, which are of particular interest for many applications, e.g. for space propulsion systems such as the VASIMR engine. A number of coils with MgB2 tapes are being built. In this paper we present results of the test of a 14 cm bore solenoid wound with 400 meters of multifilament, copper stabilized tape. The magnet was tested in a cryocooled vacuum chamber and it reached 175 A at 16 K with a central B0 of 1 Tesla. [ABSTRACT FROM AUTHOR]

For large-scale electric power applications of MgB2 wire, especially at AC environments, development of nonmagnetic sheath material is essential. In this study, Cu-sheathed MgB2 wire was fabricated using the powder-in-tube method and ultra-fine Mg and B precursor prepared by high-energy ball milling. Lowering the annealing temperature and shortening the annealing time effectively limit the reaction between Mg and Cu. Critical current density of the wire annealed at 700° C for 5 minutes is 4.3 × 104 A/cm² at 20 K and self-field. Adding excess Mg in precursor further enhances critical current to 250 A at 20 K and self-field. These results demonstrate the potential of Cu-sheathed MgB2 wires for large-scale applications. [ABSTRACT FROM AUTHOR]

Superconducting coils with different dimensions were manufactured via a wind-reaction process by using Fe-sheathed MgB2 wires, which were fabricated using the powder-in-tube method and ultra-fine starting precursors. Very good grain connectivity as well as high core density was obtained in Fe-sheathed wires and tapes. At 20 K and self-field, the critical current of the coil with ID 12 mm and 12 turns is 360 A, which is equivalent to the Jc of 1.8 × 105 A/cm². At 6 Tesla external magnetic field and 4.2 K, the coil with ID 14 cm and 10 turns possesses the Jc of 1 × 104 A/cm². In-field current carrying capability of MgB2 wires and tapes were further enhanced by Ti additive. These results demonstrate the potential of MgB2 superconducting wires and tapes for large-scale applications. [ABSTRACT FROM AUTHOR]

Much effort has recently been made to develop chemical methods for the manufacturing of coated conductors because of their scalability, low cost and high deposition rate. In this research, epitaxial buffer layers of Gd2Zr2O7, (GZO) have been grown on Ni substrates using a newly developed metal organic decomposition (MOD) approach. The solution prepared from metal-organic precursors was deposited on Ni substrates using the dip coating technique and then was annealed at a high temperature. Texture analysis shows full-width-at-half-maximum (FWHM) values for out-of-plane and in-plane alignments as 6.5° and 8.1°, respectively. Pole figure studies indicate a single cube-on-cube texture while SEM micrographs reveal a dense, continuous, and crack-free buffer layer. MOCVD was used to grow 1 μm YBCO film on this GZO buffered Ni substrate. A critical current, Jc, of about 1.3 MA/cm2 at 77 K and self-field was obtained on YBCO (MOCVD)/GZO(MOD)/Ni. These results give promise to using a single buffer layer for scalable coated conductors. [ABSTRACT FROM AUTHOR]

Isothermal melt texturing is currently a well established technique for manufacturing superconducting bulk materials with high trapped magnetic fields and levitation forces. The technique involves the growth of RE-123 compounds in geometries such as discs and short rods using top seeding of high temperature material such as SmBCO. The technique is relatively simple, however it yields nonuniform microstructure and variable superconducting properties throughout the length of the sample. The top half of the sample is well oriented and possesses good properties, while the bottom half suffers from misorientation, porosity and poor superconducting properties. In this work, the effects of using top and bottom seeding on microstructure and crystal orientation were studied. We also measured trapped magnetic fields throughout the thickness of the sample. In this arrangement, we found that both top and bottom parts of the sample are well oriented and the trapped magnetic fields in both halves are almost the same. These results give promise to the use of this technique to improve the superconducting properties in bulk textured YBCO. [ABSTRACT FROM AUTHOR]

A critical step in the successful fabrication of coated conductors on metal substrates is to produce cube texture substrates using the RABiTS approach. Nickel has been used as a substrate for high-current coated YBa[sub 2]Cu[sub 3]O[sub x] superconductors due to the relative ease in achieving sharp cube texture as well as chemical compatibility. High purity nickel (99.995%) samples were rolled to large deformation and annealed in 5% H[sub 2]-95% Ar atmosphere at 700°C-1100°C for various times. The cube texture was promoted by recrystallization after cold rolling. The effects of deformation reduction per pass, amount of deformation, and annealing temperature and time on the recrystallization process were investigated using XRD and EBSD techniques. These parameters have been optimized to obtain the cube texture {100}〈001〉. The sharpest cube texture (>80% of grains within 7° and >97% within 10° cube textured) was obtained for nickel cold rolled by 2% reduction per pass and annealed at 1000°C for 90 minutes. [ABSTRACT FROM AUTHOR]

A large number of melt-textured Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-x/ disk-shaped levitators have been manufactured using a seeding technique. Since DC transport current measurement is only capable of characterizing small samples, we have developed a system for measuring the component of the trapped field perpendicular to the surface of the disk (For simplicity, it will be called "trapped field".) and levitation force. The testing system is capable of measuring the distribution of magnetic field as well as the levitation force at the surface of the levitator in a relatively short time period. The magnetic field mapping can also be used to detect the granular microstructure in the levitators. The trapped magnetic fields of these levitators range between 0.45 and 0.65 T, and levitation forces are from 25 and 35 N. Also, the levitation force and the maximum trapped field values are found to correlate with each other. [ABSTRACT FROM PUBLISHER]

The use of high T/sub c/ SQUID (HTSQUID) magnetometers for magnetocardiography (MCG) and nondestructive testing (NDT) requires effective shielding from magnetic noise fields. The authors have investigated the shielding characteristics of high-T/sub c/ superconducting (HTS) material and developed a compact, portable system consisting of several HTS components. A process for fabricating these components out of Bi-Pb-Sr-Ca-Cu-O has been developed. Tubes and disks of various sizes have been formed by cold isostatic pressing (CIP) and sintered at reduced oxygen pressures. The HTS tubes exhibit shielding factors of up to 10/sup 3/ at low frequencies. A novel technique for fabricating superconducting flux transformers (specifically, first-order gradiometers) has also been developed. The flux transfer efficiencies of these first-order gradiometers have been evaluated. The tubes, gradiometers, and flux focusers have been incorporated into an HTSQUID setup. The authors find that the low-frequency noise rejection obtained in their setup is very promising for potential MCG and NDT applications in an unshielded environment. [ABSTRACT FROM PUBLISHER]