Search

We found that the rapid decline of SFR density from z = 1 to z = 0 is accompanied by a rapid decline of the contribution of infrared (IR) galaxies [1]. Making use of FUV (GALEX) and FIR (IRAS/Spitzer) data, we have established a method to estimate the star-formation luminosity function (LF), that is a LF of galaxy luminosity produced by newly formed stars [1]. In this work, we have calculated the distribution function of SFR of galaxies (SFR function) as a function of redshift at z = 0–1 from UV and FIR selected galaxies in the CDFS. We found that, though the FUV- and FIR-based SFR functions agree until z = 0.7, the FUV-based one becomes significantly lower than FIR based one at z = 1. As for integrated value, this means that the SFR density is at least 40% underestimated, even after adding the contribution from obscured star formation. [ABSTRACT FROM AUTHOR]

To investigate the effect of neutron irradiation on superconducting properties, a collaboration network was established among superconducting material engineering and neutronics fields. Within the framework, irradiation test of Nb3Sn and Nb3Al wires by 14 MeV fusion neutron was planned and carried out at Fusion Neutronics Source in Japan Atomic Energy Agency. After the irradiation, critical current and critical magnetic field were measured with 28 T hybrid magnet at Institute for Metals Research in Tohoku University. The irradiation to 3.52×1020 n/m2 showed a slight increase of the critical current of the Nb3Sn wire, and the irradiation to 1.78×1021 n/m2 made the critical current appreciably larger. Regarding the critical magnetic field, no clear change was observed. In the case of Nb3Al wire, a sample irradiated to 1.78×1021 n/m2 showed no increase of the critical current below 200 A which was the limit of the power supply. As for the critical magnetic field, there was no clear improvement similar to the Nb3Sn wire. The increase of the critical current would be caused by knock-on effect of the fast neutron. [ABSTRACT FROM AUTHOR]

We have succeeded in making a superconducting V—Ti alloy multifilament wire using the diffusion reaction between constituent pure-metal subelements, which can omit the melt-and-casting step and may reduce the fabrication cost. A monofilament billet prepared by restacking hexagonal Ti/V composites in a Cu/V tube and a multifilament billet by re-stacking such Cu/V/(Ti/V) composites in a Cu tube were hydrostatically extruded and drawn down to wires. Four kinds of heat treatment were investigated, with respect to mi-crostructure and superconducting properties; (1) an alloying heat treatment (HTalloy) which is carried out at the final size (‘fs-HTalloy’), (2) HTalloy is followed by cold-working (W) down to the final size (‘HTalloy+W1’), (3) an precipitation heat treatment (HTprec) is carried out after the W stage (‘HTalloy+W1+HTprec’) and (4) an intermediate HTprec is carried out during the W stage coming after the HTalloy stage (‘HTalloy+W1+HTprec+W2’). The ‘HTalloy+W1+HTprec+W2’ treatment was found to be most effective in enhancing the critical current densities (Jc), despite the HTprec treatment having slightly degraded the critical temperature (Tc) and critical magnetic field (Bc2). The highest Bc2 was obtained using the ‘HTalloy+W1’ treatment, irrespective of the HTalloy temperatures. [ABSTRACT FROM AUTHOR]

A glass fiber reinforced plastic (GFRP) with cyanate ester resin was fabricated and neutron irradiation tests up to 1×1022 n/m2 of fast neutron with over 0.1 MeV energy were carried out in fission reactor. The fabrication process of cyanate ester GFRP was established and a collaboration network to perform investigations on irradiation effect of superconducting magnet materials was constructed. Three kinds of samples were fabricated. The first was CTD403 GFRP made by NIFS, the second was (cyanate ester+epoxy) GFRP provided by Toshiba, and the last was CTD403 GFRP made by Toshiba. The irradiation was carried out at JRR-3 in Japan Atomic Energy Agency using Rabbit capsules. After the irradiation, short beam tests were conducted at room temperature and 77 K and interlaminar shear strength (ILSS) was evaluated. The irradiation of 1×1021 n/m2 increased ILSS a little but 1×1022 n/m2 irradiation decreased ILSS to around 50 MPa. These tendencies were observed in all three kinds of GFRPs. [ABSTRACT FROM AUTHOR]

Tightly consolidated Sn-Ta and Sn-B based alloys have been prepared by the reaction among constituent metal powders at 750–775° C. Sn-Ta and Sn-B based alloys exhibit quite similar microstructures. A small amount of Ti addition seems to improve the bonding between Ta or B particles and Sn matrix. Nb3Sn wires have been fabricated by the Jelly Roll (JR) and Multi-rod (MR) process using Sn based alloy sheet and rod, respectively. Thick Nb3Sn layers with nearly stoichiometric A15 composition are synthesized through a new diffusion mechanism between Nb and Sn based alloy. Bc2 (4.2 K)’s of 26.9 T (mid) and 26.5 T (mid) have been obtained in the JR and MR processed wires, respectively, using Sn-Ta based alloy. These wires exhibit enough non-Cu Jc to be used above 20 T and 4.2 K. Tc of JR wires using Sn-B based sheet is 18.14 K (offset) which is slightly higher than that of wires using Sn-Ta based sheet. [ABSTRACT FROM AUTHOR]

Sn-Ta based alloy buttons of different compositions were prepared by the melt diffusion process among constituent metal powders, and then pressed into plates. Meanwhile Sn-Ti based alloy plates were sliced from the melt and cast ingot. Resulting Sn-based alloy plates were rolled into thin sheets. The Sn-based alloy sheet was laminated with a Nb sheet, and wound into a Jelly Roll (JR) composite. The composite was encased in a sheath, and fabricated into a thin wire followed by the heat treatment. The application of hydrostatic extrusion is useful at the initial stage of the fabrication. The JR wires using Sn-Ta and Sn-Ti based alloy sheets show a non-Cu Jc of ∼250 A/mm2 and ∼150 A/mm2 at 20 T and 22 T, respectively, at 4.2 K. It has been found that the Nb impregnates into the Sn-based alloy layers during the reaction, and Nb3Sn layers are synthesized by the mutual diffusion between the Nb sheet and the Sn-based alloy sheet without formation of voids. Sn-Ti based alloy sheets are attractive due to their easiness of mass production. Structure and high-field performance of JR processed Nb3Sn wires prepared from Sn-based alloy sheets with different compositions are compared in this article. [ABSTRACT FROM AUTHOR]

Fuji Electric Group has developed a miniature pulse tube cryocooler (PTC) of U-shaped configuration with a specific cooling capacity of 2W at 70K and requiring 100W of electrical input power. The emphasis has been on compactness, light weight, high performance, high reliability and low cost. This PTC is for commercial applications: for example, semiconductivity and high temperature superconductivity (HTS) devices used in wireless telecommunication systems and imaging sensors. The dimensions of the PTC have been reduced to 246mm wide by 232mm high and a weight of 8.5kg as integral configurations. The linear compressor motor uses two sets of moving coils to drive twin pistons supported by flexure bearings in a dual opposed configuration. The phase shifter, consisting of an inertance tube and reservoir tank, has been optimized. We produced and tested a prototype reduced-cost PTC. The prototype has a cooling capacity greater than 2.5W at 70K with 100W of electrical input power. The vibration of the cold head is less than 2 micrometers (peak to peak) when the hot-end side flange of the expander is fixed. This paper describes in detail its performance including inclination and vibration. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

As a large-scale plasma experimental device is planned and designed, the importance of investigations on irradiation effect of 14 MeV neutron increases and an experimental database is desired to be piled up. Recently, intense streaming of fast neutron from ports are reported and degradation of superconducting magnet performance is anticipated. To investigate the pure neutron effect on superconducting magnet materials, a cryogenic target system was newly developed and installed at Fusion Neutronics Source in Japan Atomic Energy Research Institute. Although production rate of 14 MeV neutron is not large, only 14 MeV neutron can be supplied to irradiation test without gamma ray. Copper wires, superconducting wires, glass fiber reinforced composites are irradiated and the irradiation effects are characterized. At the same time, sensors for measuring temperature and magnetic field are irradiated and their performance was investigated after irradiation. This paper presents outline of the cryogenic target system and some irradiation test results. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Design activity of International Thermonuclear Experimental Reactor clarifies intense neutron streaming from ports for neutral beam injectors. Energy spectrum of the streaming is very wide and 14 MeV neutron and gamma ray are the typical radiations. Large amount of glass fiber reinforced plastics will be used in a superconducting magnet system as an electric insulation material and a support structure, for such organic material is easy to manufacture, and light and cheap. In this report, effects of 14 MeV neutron and gamma ray irradiation on interlaminar shear strength and fracture mode are investigated using G-10CR small specimen of which configuration was proposed as a standard for evaluation of the interlaminar shear strength. A short beam test under three point bending was conducted at room temperature and 77 K. Neutron fluence of 3.91 × 1019 n/m2 was irradiated and the specimens did not show clear degradation of the strength. On the other hand, gamma ray irradiation of 1 MGy made the specimen weaker and 10 MGy caused delamination. Most of the specimens showed both of interlaminar cracking and bending fracture, but some specimens were fractured with irregular shear occurred on the planes connecting loading point and supporting points. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A Sn+Ta+Cu mixed powder was naturally shrunk at 750°–800°C in a crucible to form a tight and ductile ingot. The ingot was pressed into a plate, and then fabricated into a thin sheet. The optimum Ta concentration in the mixed powder and the reaction temperature of the mixed powder was ∼25 at%Ta and ∼775°C, respectively. The Sn-Ta-Cu sheet was laminated with a Nb sheet and wound around a Nb-3.3 at%Ta rod to form a Jelly Roll composite. The composite was encased in a Nb-3.3 at%Ta sheath and fabricated into a wire without intermediate annealing. The wire was heat treated at 700°–800°C, where a small amount of Cu addition to the mixed powder decreases the heat treatment temperature. In the present study, the effect of a small amount of Ti addition to the Sn-Ta-Cu sheet has been studied. The Ti addition produces a more tightly shrunk ingot and a good workability into the sheet. The Ti addition appreciably increases the non-Cu Jc of the wire in entire applied field range. The Ti addition has been found to enhance the reaction between Sn-Ta-Cu and Nb sheets to form (Nb.Ta)3Sn layers increasing their areal fraction in the wire. The wire with 3 at%Ti addition to the Sn-Ta-Cu sheet shows a non-Cu Jc of ∼150 A/mm2 at 22 T and 4.2 K after heat treatment at 725°C. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

We have tried to study low activation superconducting materials of the many V-based compound superconductors, and selected the V based Laves phase (V2(Hf,Zr)) compound because of its high upper critical field (Hc2) exceeding 20 T, its neutron irradiation resistance, and its low activation in the fusion reactor compared with those of Nb-based A15 wires. The fabrication, microstructure and superconductivity of V2(Hf,Zr) multifilamentary wire synthesized by applying a rapidly-heating/quenching (RHQ) and annealing process to the simple precursor using pure Hf and Zr mixture powder and pure V tube matrix were investigated. We found that a thick reaction layer was formed between the powder mixture filament and V matrix after the RHQ treatment and then it was increased with an increment of heating energy. Offset Tc values of samples were raised by increasing heating energy, and maximum Tc values occurred at 8.3 K. The maximum Jc value was obtained for a sample of post-annealing at 600°C for 10 h. Jc dependence on the magnetic field of the post-annealed samples was higher than that of the as-quenched sample, and the Hc2 value of the annealed sample was also improved compared to the as-quenched sample. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The (7Li,7Be) charge-exchange spin-flip reaction was for the first time used to deduce the distribution of the B(M1) reduced matrix elements for the photodisintegration of deuteron from the analogous B(GT) distribution. The obtained distribution is in agreement with recent photodisintegration measurements and effective-field calculations. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Fuji Electric has developed a pulse tube cryocooler (PTC) with in-line configuration with a cooling capacity of 3 W at 70 K and requiring 100 W of electrical input power. The emphasis has been on compactness, lightweight, high performance and low cost. In particular, the dimensions of the PTC have been reduced to a width of 190 mm and a height of 300 mm. Presently, we are developing a U-shaped PTC based on the technology of the in-line PTC. The advantage of the U-shaped PTC is that the cold head is located at the end for easy accessing. The key issue for developing the U-shaped PTC is the design of the flow straightener at the cold head. As a first step in the development we visualized the inside of the pulse tube by using particle image velocimetry (PIV). The design of the flow straightener is based on the visualization results. Preliminary tests indicated that the cooling performance of the U-shaped PTC is 2 W at 70 K while requiring 51 W PV power. We will present the test results on the U-shaped PTC as well as the in-line PTC. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Nb3(Al,Ge) conductors prepared from multifilamentary Nb/Al-25at%Ge precursors with a diffusion reaction process at temperatures around 1400°C, have shown critical current density (Jc) in excess of 300 A/mm2 at 21 T and 220 A/mm2 at 23 T at 4.2 K. The diffusion spacing between the Nb and Al-Ge was not required to be reduced down to sub-micron order, which is better to reduce the fabrication difficulties. With large diffusion spacing, the A15 phase formed in equilibrium together with large region of o-phase. The A15 phase was quite Nb-rich. The attainable upper critical field (Hc2) exceeds 28.5 T, which is about 2 T larger than that of the so-called RHQT Nb3Al. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Aiming at further improvement of high-field critical current density, Jc, in the Nb3Al conductors, Si addition was attempted. To fabricate the Nb3(Al,Si) conductors, we used two times the rapid-heating and quenching (RHQ) technique. First, drawability of the Nb/Al-Si composite wire has been improved by specially using the RHQ technique at an early stage of the precursor fabrication, where only the Al-alloy core is rapidly solidified from the molten state to form a fine microstructure of the core without any reaction with the Nb. This process makes the subsequent restacking and drawing process easier. Using this technique, multifilamentary Nb/Al-Si precursors with piece length of 30 m have been successfully fabricated at our laboratory workshop. For the prepared precursors, another RHQ was attempted for the formation of the high stoichiometric A15 phase. With increasing Si content, the upper critical field was enhanced, while providing the high Jc property in high magnetic fields such as 150 A/mm2 at 25 T, 4.2 K. Meanwhile, with Si additions of 2 at% to the core, metastable BCC Nb(Al,Si)ss phase was formed by the second RHQ process. This phase can be transformed to the A15 phase by a subsequent annealing around 800°C. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Fabrication and high-field performance of (Nb,Ta)3Sn conductors through a new Jelly Roll process using Sn-Ta sheet are reported. A mixed powder of Sn and Ta (Ta/Sn ratio=3/7 and 1/3) with or without a small amount of Cu addition was melted at 800°C in vacuum. The resulting Sn-Ta alloy was rolled into sheets 100 and 200μm in thickness. The Sn-Ta sheet was laminated with a Nb foil of the same thickness, and wound around a Nb-4at%Ta rod forming a Jelly Roll composite. The composite was encased in a Nb-4at%Ta tube, and then fabricated into a wire without intermediate annealing. The wire with no Cu addition to the Sn-Ta sheet and reacted at 900°C showed a non-Cu Jc of 100–120A/mm2 at 23T and 4.2K. The non-Cu Jc of the wire at 2.1K and 25T reached 100A/mm2, the upper critical field of the wire being 28.4T. A small amount of Cu addition to the Sn-Ta sheet significantly reduced the reaction temperature, and produced a non-Cu Jc of 100–120A/mm2 at 22T and 4.2K after the reaction at 775°C. Structure characterization of the new Jelly Roll-processed (Nb,Ta)3Sn wire is also described. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Thick and uniform Nb[sub 3]Sn layers containing Ta with excellent high-field performance are synthesized through the reaction between a Ta-Sn core and a Nb-based alloy sheath. A small amount of Cu addition to the core reduces the reaction temperature. The effect of amount of Cu addition to the core on the reaction temperature, microstructure and high-field performance of the conductor has been studied changing the Ta/Sn composition ratio of the core. A variety of J[sub c] versus magnetic field performance has been obtained by adjusting the amount of Cu addition to the core and the reaction temperature in the present Nb[sub 3]Sn conductors. Furthermore, the effect of the sheath material on the structure and high-field performance of the conductor has been studied. Results obtained in the Nb-2at%Ti sheath specimen were compared with those obtained in the Nb-4at%Ta sheath specimen. A clear line composed of Cu-Ti precipitates separates the Nb[sub 3]Sn layer into two zones, when a small amount of Cu is added to the core of the Nb-2at%Ti sheath specimen. Nb-4at%Ta sheath provides appreciably better high-field performance in the conductor than Nb-2at%Ti sheath does. [ABSTRACT FROM AUTHOR]

We present number counts and clustering properties of millimeter-bright galaxies uncovered by the AzTEC camera mounted on the Atacama Submillimeter Telescope Experiment (ASTE). We surveyed the AKARI Deep Field South (ADF-S), the Subaru/XMM Newton Deep Field (SXDF), and the SSA22 fields with an area of ∼0.25 deg2 each with an rms noise level of ∼0.4-1.0 mJy. We constructed differential and cumulative number counts, which provide currently the tightest constraints on the faint end. The integration of the best-fit number counts in the ADF-S find that the contribution of 1.1 mm sources with fluxes ≥1 mJy to the cosmic infrared background (CIB) at 1.1 mm is 12-16%, suggesting that the large fraction of the CIB originates from faint sources of which the number counts are not yet constrained. We estimate the cosmic star-formation rate density contributed by 1.1 mm sources with ≥1 mJy using the best-fit number counts in the ADF-S and find that it is lower by about a factor of 5-10 compared to those derived from UV/optically-selected galaxies at z∼2-3. The average mass of dark halos hosting bright 1.1 mm sources was calculated to be 1013-1014 M⊙. Comparison of correlation lengths of 1.1 mm sources with other populations and with a bias evolution model suggests that dark halos hosting bright 1.1 mm sources evolve into systems of clusters at present universe and the 1.1 mm sources residing the dark halos evolve into massive elliptical galaxies located in the center of clusters. [ABSTRACT FROM AUTHOR]