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Vacuum Insulation and Achievement of 980 keV,185 A/m^2 H-Ion Beam Acceleration at jaea for the ITER Neutral Beam Injector

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Plasma Science and Technology 2013年第2期15卷 179-183页

作者： Hiroyuki TOBARI Masaki TANIGUCHI Mieko KASHIWAGI Masayuki DAIRAKU Naotaka UMEDA Haruhiko YAMANAKA Kazuki TSUCHIDA Jumpei TAKEMOTO Kazuhiro WATANABE Takashi INOUE Keishi SAKAMOTO Japan Atomic Energy Agency (jaea) Mukouyama 801-1 Naka Ibaraki 311-1093 Japan

Abstract Vacuum insulation of -1 MV is a common issue for the HV bushing and the accel- erator for the ITER neutral beam injector （NBI）. The HV bushing as an insulating feedthrough has a five-stage structure and each stage consists of double-layered insulators. To sustain -1 MV in vacuum, reduction of electric field at several triple points existing around the double-layered insulators is a critical issue. To reduce electric field simultaneously at these points, three types of stress ring have been developed. In a voltage holding test of a full-scale mockup equipped with these stress rings, 120% of rated voltage was sustained and the voltage holding capability required in ITER was verified. In the MeV accelerator, whose target is the acceleration of a H- ion beam of 1 MeV, 200 A/mS, the gap between the grid support was extended to suppress breakdowns triggered by electric field concentration at the edge and corner of the grid support. This modi- fication improved the voltage holding capability in vacuum, and the MeV accelerator succeeded in sustaining -1 MV stably, b-~rthermore, it appeared that the H- ions beam was deflected and a part of the beam was intercepted at the acceleration grid, This causes high heat load on the grids and breakdowns during beam acceleration. To suppress the direct interception, a new grid was designed with proper aperture displacement based on a three dimensional beam trajectory analysis, As a result, 980 keV, 185 A/ms H- ion beam acceleration has been demonstrated, which is close to the ITER requirement.

关键词： neutral beam injector (NBI) negative ion beam HV bushing vacuum insu-lation

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Chemical studies of the transactinlde elements at jaea

Chemical studies of the transactinlde elements at JAEA

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The 6th China-Nuclear Physics Symposium

作者： Y. Nagame Advanced Science Research Center Japan Atomic Energy Agency (JAEA) TokaiIbaraki 319-1195Japan

Studies on the chemical properties of the transactinide elements (Z ≥ 104) offer unique opportunities to obtain information about trends in the periodic table of the elements at the limits of nuclear stability, and to assess the magnitude of the influence of relativistic effects on chemical properties. From the calculations of electron configurations of heavier elements, it is predicted that sudden changes in the structure of electron shells may appear due to relativistic effects which originate from the

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Chemical studies of the transactinide elements at jaea

Chemical studies of the transactinide elements at JAEA

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6th China-Japan Nuclear Physics Symposium

作者： Y. Nagame Advanced Science Research Center Japan Atomic Energy Agency （JAEA） Tokai Ibaraki 319-1195 Japan

＜正＞Studies on the chemical properties of the transactinide elements （Z ≥ 104） offer unique opportunities to obtain information about trends in the periodic table of the elements at the limits of nuclear stability, and to assess the magnitude of the influence of relativistic effects on chemical properties. From the calculations of electron configurations of heavier elements, it is predicted that sudden changes in the structure

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Low-Energy Spin Excitations in Detwinned FeSe

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Chinese Physics Letters 2024年第6期41卷 112-118页

作者：刘瑞鲜 Mitsutaka Nakamura Kazuya Kamazawa 鲁兴业 Center for Advanced Quantum Studies School of Physics and AstronomyBeijing Normal UniversityBeijing 100875China J-PARC Center Japan Atomic Energy Agency(JAEA)TokaiIbaraki 319-1195Japan Research Center for Neutron Science and Technology Comprehensive Research Organization for Science and SocietyTokaiIbaraki 319-1106Japan

Antiferromagnetic spin fluctuation is regarded as the leading driving force for electron pairing in high-Tc *** iron-based superconductors,spin excitations at low energy range,especially the spin-resonance mode at ER~5kBTc,are important for understanding the ***,we use inelastic neutron scattering(INS)to investigate the symmetry and in-plane wave-vector dependence of low-energy spin excitations in uniaxial-strain detwinned Fe *** low-energy spin excitations(E<10 meV)appear mainly at Q=(±1,0)in the superconducting state(T9K)and the nematic state(T90 K),confirming the constant C_(2) rotational symmetry and ruling out the C_(4) mode at E≈3 meV reported in a prior INS ***,our results reveal an isotropic spin resonance in the superconducting state,which is consistent with the s±wave pairing *** slightly higher energy,low-energy spin excitations become highly *** full width at half maximum of spin excitations is elongated along the transverse *** Q-space isotropic spin resonance and highly anisotropic low-energy spin excitations could arise from dyz intra-orbital selective Fermi surface nesting between the hole pocket aroundΓpoint and the electron pockets centered at MX point.

关键词： excitation symmetry slightly

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Prediction of Turbulent Flow Structure in a Fully Developed Rib-Roughened Narrow Rectangular Channel

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Journal of Thermal Science 2009年第2期18卷 126-136页

作者： Md.Shafiqul Islam M.Kaminaga R.Hino M.Monde Atomic Energy Research Establishment Japan Atomic Energy Agency (jaea) Department of Mechanical Engineering Saga University

Fully developed turbulent water-flow structure over one-side repeated-ribs in narrow two-dimensional rectangular channels was investigated experimentally by Particle Image Velocimetry （PIV） and analytically by the standard k-ε and nonlinear k-ε turbulent models. Two rib-pitch to height ratios （p/k） of 10 and 20 were investigated while the rib height was held constant at 4 mm. The rib height-to-channel equivalent diameter ratio （k/De） was 0.1. The streamwise mean velocity and turbulent kinetic energy distributions at six selected axial stations from the center rib for the two Reynolds number （Re） of 7,000 and 20,000 were obtained and compared with the predicted one. The performance ability in predicting separating and reattaching turbulent water-flow between the standard K-ε and nonlinear k-ε models had yielded no clear conclusion. A large-scale turbulent eddy was generated by the rib promoter and then propagated into the mainstream flow, which led to the deformation of the velocity profile. The turbulent kinetic energy was increased about two times higher at p/k = 20 than that at p/k =10 under the two Reynolds numbers. The effect of the p/k value and the Reynolds number （Re） on reattachment length （XR） was investigated and showed that the p/k and Re had no significant effect on the reattachment length beyond a critical value of Re = 15,000 where XR was found to be approximately 4 times of the rib height under water-flow condition.

关键词： Turbulent water-flow structure repeated-ribs narrow rectangular channels two-dimensional analysis reattachment length

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Tuning of RF amplitude and phase for the drift tube linac in J-PARC

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Chinese Physics C 2009年第7期33卷 577-582页

作者：沈国保 Masanori Ikegami Japan Atomic Energy Agency(jaea) 2-4 Shirakata-Shirane High Energy Accelerator Research Organization(KEK)

The J-PARC linac has three DTL tanks to accelerate the negative hydrogen ions from 3 MeV to 50 MeV. The RF phase and amplitude are adjusted for each cavity with a phase scan method within the accuracy of 1° in phase and 1% in amplitude. The experimental results show a remarkable agreement with the numerical model within a suffcient margin in the tuning of the last two DTL tanks. However,a notable discrepancy between the experiment and the numerical model is seen in the tuning of the first DTL tank. After studying with a three-dimensional multi-particle simulation,the generation of the low energy component and the pronounced filamentation are identified as the main causes of the discrepancy. The optimization of the tuning scheme is also discussed to attain the tuning goal accuracy for the first DTL tank.

关键词： high-intensity beam drift tube linac signature matching J-PARC

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Structure of exotic nuclei by large-scale shell model calculations

Structure of exotic nuclei by large-scale shell model calcul...

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6th China-Japan Nuclear Physics Symposium

作者： Y.Utsuno jaea

＜正＞One of the most intriguing features in the structure of exotic nuclei is the so-called the disappearance of the magic number, which denotes that nuclei around the magic number have no typical magic structure such as a high 2^+ energy level. The N=20 region has been most extensively studied about the disappearance both experimentally

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Empirical correlations for predicting the self-leveling behavior of debris bed

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Nuclear Science and Techniques 2013年第1期24卷 43-52页

作者： CHENG Songbai YAMANO Hidemasa SUZUKI Tohru TOBITA Yoshiharu NAKAMURA Yuya ZHANG Bin MATSUMOTO Tatsuya MORITA Koji Advanced Nuclear System R&D Directorate Japan Atomic Energy Agency (JAEA) Department of Applied Quantum Physics and Nuclear Engineering Kyushu University

Studies on the self-leveling behavior of debris bed are crucial for the assessment of core-disruptive accident (CDA) occurred in sodium-cooled fast reactors (SFR). To clarify this behavior over a comparatively wider range of gas velocities, a series of experiments were performed by injecting nitrogen gas uniformly from a pool bottom. Current experiments were conducted in a cylindrical tank, in which water, nitrogen gas and different kinds of solid particles, simulate the coolant, vapor (generated by coolant boiling) and fuel debris, respectively. Based on the quantitative data obtained (mainly the time variation of bed inclination angle), with the help of dimensional analysis technique, a set of empirical correlations to predict the self-leveling development depending on particle size, particle density and gas injection velocity was proposed and discussed. It was seen that good agreement could be obtained between the calculated and experimental values. Rationality of the correlations was further confirmed through detailed analyses of the effects of experimental parameters such as particle size, particle density, gas flow rate and boiling mode. In order to facilitate future analyses and simulations of CDAs in SFRs, the obtained results in this work will be utilized for the validations of an advanced fast reactor safety analysis code.

关键词：自流平行为模拟冷却水预测气体速度注入氮气粒子密度实验值

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Demonstrations of Neutron Resonance Spin Echo for Pulsed Source

Demonstrations of Neutron Resonance Spin Echo for Pulsed Sou...

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作者： M.Kitaguchi M.Hino Y.Kawabata S.Tasaki R.Maruyama T.Ebisawa jaea

INTRODUCTION:Neutron spin echo(NSE) is one of the techniques with the highest energy resolution for quasi-elastic scattering by measuring rotation of the neutron *** neutron resonance spin echo(NRSE),two resonance spin flippers(RSFs) replace a homogeneous static magnetic field for spin precession in the conventional *** RSF,which flips the spin of a neutron by exchanging energy between the neutron and an oscillating magnetic field,gives the difference of wavenumber between up- and down-spin components of the neutron.

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Land cover change detection based on satellite data for an arid area to the south of Aksu in Taklimakan desert

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Journal of Arid Land 2010年第1期2卷 14-19页

作者： Kiyoshi TSUCHIYA Tamotsu IGARSHI Muhtar QONG Japan Meteorological Consultant Association EORC Japan Aerospace Exploration Agency (JAEA) Space and Earth Information Technology School of EngineeringKyushu Tokai University

An experiment is made to detect the land-cover change in the area located to the south of Aksu in the northern Taklimakan desert through analyses of satellite data pixel by pixel basis. The analyzed data are those observed in the late summer and early autumn of 1973, 1977, 1993 and 1995. As a parameter of land-cover, SAVI (Soil Adjusted Vegetation Index) derived from the data of Landsat MSS and JERS-1 OPS (Optical Sensor) is used. The result indicates the increase of vegetation in the oasis areas, confluent area of the Yarkant and Kashgar Rivers and around reservoirs while little change occurs in the desert area. The 1973 satellite image shows the abundant flow in the Yarkant River while the river is almost dried up in the satellite images of later years. The trend of the decrease in the Hotan River flow is recognized although not so dramatic as that of the Yarkant River.

关键词： Taklimakan Desert SAVI Landsat MSS JERS-1 OPS vegetation false color landcover change

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