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ABSTRACT: The high field magnetizations of hexagonal UPd2Al3 in various field directions are investigated up to 50 Tesla (T). The angular dependence of the step-magnetization field shows a large anisotropy in the ac-plane and the spin system can be regarded as the XY-spin model except for a very small anisotropy in the c-plane. The observed step-magnetization is explained by introducing the model that the heavy Fermion state is broken by the magnetic field at the critical field and the exchange interaction is reduced by the change in the carrier density.
Physica B: Condensed Matter.
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ABSTRACT: IRFM (CEA Cadarache) and JAEA Naka have entered into a collaboration in order to test a Single Gap, Single Aperture (SINGAP) [H.P.L. de Esch, R.S. Hemsworth, P. Massmann, Updated physics design ITER-SINGAP accelerator, Fusion Eng. Des. 73 (2005) 329.] accelerator at the JAEA Megavolt Test Facility (MTF) at Naka, Japan. Whereas at the CEA testbed the acceleration current was limited to 0.1 A, at JAEA 0.5 A is available. This allows the acceleration of 15 H− beamlets in SINGAP to be tested and a direct comparison between SINGAP and Multi Aperture, Multi Grid (MAMuG) [M. Taniguchi, T. Inoue, N. Umeda, M. Kashiwagi, K. Watanabe, H. Tobari, M. Dairaku, K. Sakamoto, Acceleration of ampere class H− ion beam by MeV accelerator, Rev. Sci. Instrum. 79 (2008) 02C110.] to be made.High voltage conditioning in the SINGAP configuration has been quite slow, with 581 kV in vacuum achieved after 140 h of conditioning. With 0.25 Pa of H2 gas present in the accelerator 787 kV could be achieved. The conditioning curve for MAMuG is 200 kV higher.SINGAP beam optics appears in agreement with calculation results. A beamlet divergence better than 5 mrad was obtained.SINGAP accelerates electrons to a higher energy than MAMuG. Measurements of the power intercepted on one of the electron dumps have been compared with EAMCC code [G. Fubiani, H.P.L. de Esch, A. Simonin, R.S. Hemsworth, Modeling of secondary emission processes in the negative ion based electrostatic accelerator of the International Thermonuclear Experimental Reactor, Phys. Rev. ST Accel. Beams 11 (2008) 014202.] calculations.Based on the experiments described here, electron production by a SINGAP accelerator scaled up to ITER size was estimated to be too high for comfort.
Fusion Engineering and Design.
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ABSTRACT: This paper reports R&D progress of the MeV class accelerator, beam focussing technique and a high voltage (HV) bushing toward the ITER Neutral Beam system at JAEA. A H− ion beam of 320 mA (current density: 140 A/m2) was successfully accelerated up to 796 keV by fixing air leak in the ion source chamber caused by heat loading due to backstream positive ions. From analyses of a three-dimensional beam trajectory, a countermeasure against beamlet deflection due to space charge repulsion among beamlets was identified to compensate the deflection by proper aperture offset in the electron suppression grid. For development of the HV bushing, a half-size (Ø800 mm) mockup single stage bushing was manufactured and tested, that demonstrated the dc voltage holding capability of up to 220 kV in a condition with vacuum inside. Electrostatic analyses and design of the HV bushing are in progress, in which some design improvements are suggested to reduce electric field strength on the surface of ceramic insulator.
Fusion Engineering and Design.
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T. Suzuki,
Y. haga,
D.X. Li,
T. Matsumura,
E. Hotta,
A. Uesawa,
M. Kohgi,
T. Osakabe,
S. Takagi,
H. Suzuki, [......],
A. Mitsuda,
S. Kimura,
S. Takayanagi,
N. Wada,
A. Oyamada,
K. Hashi,
S. Maegawa,
Y.S. Kwon,
E. Vincent,
P. Bonville
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ABSTRACT: Recent progress in studies on low carrier concentration systems of magnetically ordered and non-magnetic heavy Fermion metals are discussed. Successive steps in the high field magnetisation, the magnetic structure, and the influence of high pressure are reported and the relation with the observed Fermi surface for CeP is discussed. The origin of the low carrier concentration in USb is also discussed based on the first observation of dHvA oscillations. It is also unambiguously demonstrated that the unconventional heavy Fermion state of Yb4As3 is intrinsic and not due to impurities.
Physica B: Condensed Matter.
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雅人 月岡,
俊之 大島,
修一 三上,
智之 山崎,
孝英 佐藤,
稔康 井上,
M. Tsukioka,
T Oshima,
S Mikami,
T Yamazaki,
T Sato, T Inoue
土木学会北海道支部論文報告集.
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ABSTRACT: A morphological characterization of activated AR-resin was carried out. The time and temperature effect of the EDLC (electric double layer capacitor) properties of AR-resin were investigated. In order to clarify the relation between the electric double layer capacitance and the ion mobility in the organic solvent, a computer simulation was used to calculate the possible solvation size of Et4NBF4 in propylene carbonate. The sample (HTT 700) activated at a heat treatment temperature (HTT) of 700 °C for 2 h has a specific capacitance as high as 35.27 F g−1 (equivalent to 141.08 F g−1 for a single electrode), when it is charged to 2.5 V and discharged at 1 mA cm−2. The capacitance increase by using a longer activation time at each HTT was as follows: 2.3 times at HTT 600, 1.6 times at HTT 700, 1.3 times at HTT 800 and 1.2 times at HTT 900. This variation could be forecast from image analysis using a TEM photograph. Furthermore, a possible ion size of electrolyte (Et4NBF4) in a solvent was calculated and it is related to the mobility of charge carriers in a micropore.
Carbon.
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ABSTRACT: Two dimensional radiation transport calculations have been carried out to determine radiation streaming through the ITER equatorial ports. The NBI port has been identified as the most critical. Shielding requirements were estimated to minimize the nuclear heating rates in the toroidal field (TF) coils and the activation of the cryostat, where hands-on maintenance is anticipated. The shielding efficiency of steel/water port walls was investigated as a function of port and wall dimensions and steel volume fraction. For open ports, i.e. the neutral beam injector ducts, 40–50 cm thick port walls composed of 40% SS-60% H2O–75% SS-25% H2O will reduce the TF coil heating to acceptable levels, while 60–65 cm thick walls are necessary for reducing the dose rates at ∼2 weeks after shutdown to levels of 750 μSv h−1 at the cryostat.
Fusion Engineering and Design.
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ABSTRACT: An experimental study was conducted to determine the fluid flow and heat transfer characteristics in a passage formed by two parallel rotating disks. The local heat transfer coefficients along the disk radius were measured in detail and the flow patterns between the two rotating disks were visualized by using paraffin mist and a laser-light sheet.It was disclosed that 1) the self-sustained laminar flow separation which is characteristic of the stationary disks still exists even when the disks are set in motion, giving significant influence to the heat transfer. 2) For small source flow Reynolds number, Re, and large rotational Reynolds number, Reω, rotating stall dominates the heat transfer. 3) Heat transfer for steady laminar flow occurs only when both the source-flow and rotational Reynolds numbers are small: Re < 1200 and Reω < 20.
Experimental Thermal and Fluid Science.
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Y. Ikeda,
N. Akino,
N. Ebisawa,
M. Hanada, T. Inoue,
A. Honda,
M. Kamada,
M. Kawai,
M. Kazawa,
K. Kikuchi, [......],
F. Okano,
T. Ohga,
K. Oshima,
T. Takenouchi,
H. Tamai,
Y. Tanai,
N. Umeda,
K. Usui,
K. Watanabe,
H. Yamazaki
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ABSTRACT: Modification of JT-60U to a superconducting device (so called JT-60SA) has been planned to contribute to ITER and DEMO. The NBI system is required to inject D0 beams of 34 MW for 100 s. The upgraded NBI system for JT-60SA consists of 12 positive-ion-based NBI (P-NBI) units and one negative-ion-based NBI (N-NBI) unit. The injection powers of each P-NBI and N-NBI units are 2 MW at 85 keV and 10 MW at 500 keV, respectively. On JT-60U, the long pulse operations of 30 s at 2 MW and 20 s at 3.2 MW have been achieved on the P-NBI and N-NBI units, respectively. Both units have demonstrated no injection power degradation for long pulse operation. It has been also found that the thermal time constants of the main key components with active cooling, such as the ion source of the present NBI system, are less than ∼20 s. Therefore, the pulse extension up to 100 s is expected to need some modifications mainly the power supply system. In addition, the voltage-holding capability of the negative ion source is required to be improved. The detailed technical design of the NBI system for JT-60SA is presented.
Fusion Engineering and Design.
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ABSTRACT: A source term release analysis code for high-level waste glass has been developed for simulation of long-term dissolution behavior under repository conditions. The STRAG4 code consists of models for (a) element diffusion in both the bulk glass and surface layer, (b) glass dissolution kinetics at the interface between glass and water, and (c) geochemical reactions of dissolved elements in underground water. The simulations for various conditions of glass dissolution, including a static and dynamic system, show accordance with the experimental observations even in the relatively complicated case where bentonite is present. Long-term dissolution analyses of a borosilicate waste glass were carried out as preliminary study. The calculations were achieved by considering detrimental effects due to interactions between the glass and surrounded materials which are presumed to be in a repository environment (i.e., compacted bentonite, corrosion products from the iron overpack, and underground water). The environmental conditions such as temperature and geochemical reactions are also taken into account in the calculations. The results suggest the life of the waste glass would be more than 50,000 years even if the glass surface area increased by a factor of 10 due to crack formation.
Waste Management.
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N. Umeda,
T. Yamamoto,
M. Hanada,
L. Grisham,
M. Kawai,
T. Ohga,
N. Akino, T. Inoue,
M. Kazawa,
K. Kikuchi,
K. Mogaki,
H. Yamazaki,
K. Watanabe,
Y. Ikeda
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ABSTRACT: In the negative ion based neutral beam injector (N-NBI) for JT-60U, an extension of the pulse duration up to 30 s has been intended to study quasi-steady state plasmas, where the NBI pulse duration is significantly longer than the plasma current diffusion time. Achieving long pulse injection requires a reduction of the heat load on the grids of the ion source. The ion source was modified to reduce the pressure within the grid structure by increasing the vacuum conductance of the acceleration grids. The acceleration efficiency was improved from 0.74 to 0.79. The heat load of the grounded grid, which was the main heat load of the acceleration grids, decreased from 9.2 to 7.0% at a constant arc chamber pressure of 0.3 Pa. These improvements seemed to be caused by the reduction of beam ion stripping loss. Up to now, a long pulse injection of 17 s at the power of 1.6 MW with beam energy of 366 keV was obtained by using one ion source. The temperature rise of the cooling water from the grounded grid saturated at less than 35 °C during operation, so the heat load of the grid is significantly reduced for steady state operation at this power level.
Fusion Engineering and Design.
