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Microstructures of rapidly-heated/quenched and transformed Nb& multifilamentary wires were studied by using transmission electron microscopy. Nb/AI composite wires are fabricated by a jelly-roll process. The Nb/AI composite filaments changed into Nb-AI supersaturated bcc solid solution with the rapidly-heating/quenching. The Nb-AI bcc phases consists of many crystal grains with diameters of 2-4 pm, surrounded with large-angle grain boundaries. Some spherical voids, about 0.1 micron in diameter, were also observed at the intra-and intergrains. All grain boundaries of the Nb-AI bcc phases are simple flat planes. Then, the Nb-AI bcc phases were transformed into A15 phases (grain size: 0.5-2.0 pm in diameter) with additional annealing. Secondary phases were not observed in the A15 filaments. Grain boundaries of the A15 phases show zigzag shape unlike those of the Nb-AI bcc phases, and every grain of A15 phases is an aggregation of sub-grains of 80-150 nm in diameter. Sub-grain boundaries are small-angle ones. Moreover, we found that many stacking faults formed in the A15 sub-grains in parallel with spaces of 10-20 nm. These numerous plane defects seem to be the main pinning centers in the rapidlyheated/quenched and transformed NbJAl wires. Index

In this study, we report that the transport critical current density Jc of Ba122 tapes can be significantly enhanced by using the harder stainless steel (SS)/Ag-Sn double sheath. A high Jc value of 1.4 × 105 A cm−2 (at 4.2 K and 10 T) was achieved in SS/Ag-Sn alloyed double sheathed tapes by cold pressing. Even for as-rolled tapes, the Jc exceeds the practical level of 105 A cm−2 in magnetic fields up to 10 T. More interestingly, a high Jc value of 5.5 × 104 A cm−2 at 10 T was obtained by a heat treatment with a very low temperature of 550 °C. The microstructure investigations reveal that the higher core density of the Ba122 tapes with uniform deformation and better grain alignment are responsible for the superior Jc-field performance.

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Recently, gas giant planets in nearly circular orbits with large semimajor axes (a ∼ 30-1000AU) have been detected by direct imaging. We have investigated orbital evolution in a formation scenario for such planets, based on core accretion model: i) Icy cores accrete from planetesimals at 30AU, ii) they are scattered outward by an emerging nearby gas giant to acquire highly eccentric orbits, and iii) their orbits are circularized through accretion of disk gas in outer regions, where they spend most of time. We analytically derived equations to describe the orbital circularization through the gas accretion. Numerical integrations of these equations show that the eccentricity decreases by a factor of more than 5 during the planetary mass increases by a factor of 10. Because runaway gas accretion increases planetary mass by ∼ 10-300, the orbits are sufficiently circularized. On the other hand, a is reduced at most only by a factor of 2, leaving the planets in outer regions. If the relative velocity damping by shock is considered, the circularization is slowed down, but still efficient enough. Therefore, this scenario potentially accounts for the formation of observed distant jupiters in nearly circular orbits. If the apocenter distances of the scattered cores are larger than the disk sizes, their a shrink to a quarter of the disk sizes; the a-distribution of distant giants could reflect outer edges of the disks in a similar way that those of hot jupiters may reflect inner edges.

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In the process that leads a flawless Nb 3 Sn round strand to become part of a Rutherford cable first, and of a coil next, the same cabling process affects strands of different kinds in different ways, from filament shearing to subelement merging to composite decoupling. Due to plastic deformation, after cabling the filament size distributions in a strand usually change. The average filament size typically increases, as does the width of the distribution. This is consistent with the low field transport current of strands in cables being typically lower and less reproducible than for round strands [1]. To better understand the role of filament size in instabilities and to simulate cabling deformations, strands to be used in cables can be tested by rolling them down to decreasing sizes to cover an ample range of relative deformations. A procedure is herein proposed that uses both microscopic analysis and macroscopic measurements of material properties to study the effects of deformation.Index Terms-Critical current density, magnetic instability, Nb 3 Sn, Rutherford cable.