Cu-Nb/Nb 3 Sn wires have high mechanical strength and large compressive residual strain. In this study, we successfully developed thin Cu-Nb/Nb 3 Sn round wires and tapes to avoid the critical current ( I c ) degradation caused by damage of brittle Nb 3 Sn filaments in React-and-Wind (R&W) process with small bending diameters. Both the Cu-Nb/Nb 3 Sn round wires of 0.45 mm diameter and the tapes of 0.40 mm thickness had I c increase by pre-bending treatments up to bending strains of ±0.6% in the Nb 3 Sn filamentary area including the tin-diffusion barrier. The pre-bent tapes of thicknesses 0.9–0.25 mm (aspect ratio 1.5–10.2) showed higher I c characteristics than as-reacted tapes independently of magnetic field directions. The R&W spiral coils of 39 mm diameter, which were wound with the pre-bent round wire of 0.45 mm diameter and the pre-bent tape of 0.48 mm thickness, retained higher I c - B characteristics than those of the W&R spiral ones.
This paper presents, for the first time, a novel thin heat spreader based on COunter Stream Mode OScillating flow (COSMOS) concept. The heat spreader fabricated by silicon micromachining has 14 folded meander Si groove with total length of 700 mm, width of 575 /spl mu/m, depth of 400 /spl mu/m and the wall thickness between the adjacent channels of 150 /spl mu/m which is connected to two piezoelectric type pumps. The total device size was 86 /spl times/ 57 mm/sup 2/ and the effective cross-section of the heat-pipe was 0.5 /spl times/ 10 mm/sup 2/. The device demonstrated the temperature gradient of 500 K/m and the heat transport rate of 20 W with using water as working fluid. From these results, the effective thermal conductivity was calculated to 9/spl times/10/sup 3/ W/m/spl middot/K which is 23 times larger than that of copper.
Small size ( 2mm-long ) GaAs/AlGaAs directional couplers, with crosstalk as low as -16 dB at λ=1.3μm without a requirement for precise device dimensions control, have been achieved by using alternating Δβ technique.
A Rutherford flat cable composed of sixteen 0.8-mm-diameter Nb 3 Sn strands with CuNb-reinforced stabilizers (CuNb/Nb 3 Sn) has been developed for use as an outsert for a 47-T hybrid magnet. To guarantee the safety of the magnet in the event of a quench, the low residual resistance ratio characteristic of arc-melted-in-situ CuNb composite had to be improved upon, and to obtain high electric conductivity, a new CuNb fabrication method using a Nb rod was attempted. The thermal runaway characteristics of chemical vapor deposition- YBa 2 Cu 3 O 7-δ (Y123) coated-conductor tapes with varying Cu stabilizer thicknesses were measured in magnetic fields of up to 10 T at temperatures ranging from 17 to 60 K. It was found that the ratio of the thermal runaway over-current to the critical current decreases as temperature decreases and that thermal runaway occurs just above the critical current level at 5 K. The properties of a cryogen-free, 20-T superconducting outsert for a 47-T hybrid magnet utilizing CuNb/Nb 3 Sn Rutherford flat cables and Y123 tapes and having a room temperature bore of 400 mm were investigated.
Corundum-structured iridium oxide (α-Ir2O3), showing p-type conductivity, is a strong candidate to form high-quality pn heterojunctions with α-Ga2O3. We fabricated α-Ir2O3/α-Ga2O3 pn heterojunction diodes and they showed well-defined rectifying current-voltage (I-V) characteristics with the turn-on voltage of about 2.0 V. The band alignment at the α-Ir2O3/α-Ga2O3 interface was investigated by X-ray photoemission spectroscopy, revealing a staggered-gap (type-II) with the valence- and conduction-band offsets of 3.34 eV and 1.04 eV, respectively. The total barrier height for electrons was about 2.4 eV, which reasonably agreed with the turn-on voltage in the I-V characteristics. This means that electrons are mainly attributed to electrical conduction around the turn-on voltage.
Using a new LPE growth technique, an InGaAsP/InP planar buried heterostructure laser diode (PBH-LD) has been realised in 1.3 and 1.5 μm wavelength regions. As a result of the effective carrier confinement, CW threshold currents as low as 8.5 mA and 13 mA have been obtained in 1.3 and 1.5 μm PHB-LDs, respectively, at room temperature.
By pumping a small-core single-mode silica fibre with a 1.32 μm CW Nd:YAG laser, continuous-wave Raman amplification of InGaAsP laser diode light, with unsaturated gain as high as 21 dB, has been obtained in both backward as well as forward pumping configurations.
The threshold current dispersion, slope efficiency and lasing wavelength of vertical-to-surface transmission electrophotonic devices with vertical cavities are investigated. The critical number of output distributed Bragg reflectors (DBRs) required to overcome the disturbance due to back-surface reflections for surface-emitting-laser (SEL) structure devices is clarified.
The new high magnetic field research laboratory network is recognized as one of the Japanese Master Plans of Large Research Project by the Science Council of Japan. Recently, the project of the 25 T cryogen-free superconducting magnet (25 T-CSM), which is operated under a conductive cooling condition by cryocooler, was approved under the high magnetic field research laboratory network. We adopted a high strength CuNb/Nb 3 Sn Rutherford cable with a prebending treatment for the middle section coils of the 25 T-CSM. The central magnetic field of 14 T is generated by the operational current of 851 A by the Nb3Sn middle section and NbTi outer section coils in a 300 mm bore. The induced maximum hoop stress in the CuNb/Nb3Sn section is about 250 MPa. In addition, the 11.5 T high temperature superconducting insert coil is also designed using Gd123 tapes. Therefore, a total central magnetic field of 25.5 T can be achieved.
