Papers by Keyword: Neutron

Abstract: Synchrotron X-rays have the advantage of being a micro beam, allowing us to create detailed stress maps. However, due to a dendritic structure, measuring the residual stresses of a welded part is difficult. This challenge is caused by the difference in the positions of the diffracted crystal grains. To address this problem, we proposed a double exposure method. In this presentation, the double exposure method was applied to measure the residual stress of the plate that was cut from the welded pipe. Detailed strain maps under a plane stress state were obtained. Conversely, the residual stress distributions of the welded pipe under a triaxial stress state were measured using neutrons. From these results, the detailed stress maps of the root part of the butt-welded pipe were made up by the complimentary use of the synchrotron X-rays and neutrons. The results can significantly explain theinitiation and propagation of stress-corrosion cracking. We name this analysis method the quantum beam hybrid stress analysis.

Abstract: KENS-II is the second generation of the spallation neutron source at KEK which was operated from December 1, 2000 to March 22, 2006 supplying neutron beam to the neutron spectrometers of material science. The present paper reviews history of the KENS-II from its design to removal together with its performance for the neutron scattering experiments.

Abstract: Neutron bombardment on semiconductor material causes defects, one such primary physical effect is the formation of displacement defects within the crystal lattice structure, and such defects effectively decrease the mean free path and thus shorten the recombination time. Ionizing radiation causes creation of electron-hole pair in the gate oxide and in parasitic insulating layers of the MOS devices. Calculations show increase of the dark current in depletion region caused by a single neutron. Determination of energy and angular distribution of primary knock on atoms, with 14 MeV neutron irradiation in silicon are presented.

Abstract: 4H-SiC Schottky barrier diodes (SBDs) were irradiated to neutron fluence of 3.55 x10¹⁶ cm^-2 and 6.6 x 10¹⁵ cm^-2 (15,000 kGy) electrons respectively. In general, characterization of the irradiated samples show that the current characteristics of the diodes decreased. The performance of Schottky gate contact is less for electron irradiated sample compared to neutron irradiated sample. The d-spacing, crystallite sizes and lattice strains were calculated from X-ray diffraction (XRD) measurements. SiC Schottky interface damage and radiation defects, as observed in atomic force microscopy (AFM) topography and scanning electron microscope (SEM) morphology images is possibly the main reason for this reduction in performance.

Abstract: Silicon is always the dominant semiconductor material of the modern semiconductor industry. This is as silicon can retain its semiconductor characteristics even at a higher temperature while the other semiconductor materials can't. However, when a silicon device is exposed to a flux of energetic radiation or particles, the effects from the radiation and the induced secondary particles can cause several degradation of the device performance. For the purpose of investigate the resultant effects from the bombardment of neutrons and the behavior of secondary charged particles in the silicon model, the neutron displacement defect was measured in situ and then followed by the simulation based on Monte Carlo method. The bombardment of neutron in the silicon model produce at least three secondary particles, which are alpha ˸α˹ particles, proton (p) particles and silicon recoil atoms, through the reactions of ˸̾˼α˹˼˰˸̾˼̀˹˰and neutron scattering respectively. The kinetic energy and range of these charged particles are different among themselves, and thus the probability of hitting and degradation effects in the silicon materials are varies. The simulation calculation showed that ˸̾˼α˹˰reaction induced soft error cross section of about 8.7 x 10^-14 cm² and for recoil atoms, it is about 2.9 x 10^-15 cm². There was no error of the silicon device configuration induced by proton particles until 10¹⁰ n/cm².neutron fluence. It can be concluded that the largest portion of error in the silicon model is induced by the secondary alpha ˸α˹ particles.

Abstract: With the booming of Cloud Compute, OpenStack has been more widely used in Data Center, but in tradition deployment of OpenStack, the traffic must traverse network node to get routing decision. So the network node would be a bottle-neck due to the increasing amount of data flow. In order to solve this problem, this paper propose an extensible design, we create a internal virtual router in each compute node, the internal virtual router just can process the East-West traffic in lay2. With the help of distributed router, the East-West traffic can be delivered directly from the source hypervisor to the destination hypervisor, no longer need to traverse the router in network node to get routing decision, Therefore, North-South and East-West traffic don't impact each other anymore. North-South traffic enjoys all the bandwidth of router in network node exclusively, hence reduce the load of the network node. Experiment results show that OpenStack with distributed router has a much better performance evaluation than original OpenStack. This will dramatically increase the total bandwidth, and also bring other advantages.

Abstract: The paper presents neutron diffraction analysis and X-ray investigation of ordered alloys Ni₃(Mn,Ti) within the concentration range from 0 to 12.5 at.% Ti. The significant effect of the third alloying element Ti on the atomic long-range order was observed in superstructure L1₂ of alloy Ni₃Mn. Experimental study has showed that a rapid quenching in ice water does not provide disordered Ni₃(Mn,Ti) alloys. The two-phase region of internmetallic bonds was detected in compounds L1₂ and D0₂₄. The paper presents results estimation of electrical resistivity, normal and abnormal values of hall coefficient, Nernst–Ettingshausen effect, thermal electromotive force, and average atomic magnetic moment in quenched and annealed Ni₃(Mn,Ti) alloys. Positive values of abnormal hall coefficient and Nernst–Ettingshausen effect were detected that confirms the predominant contribution of antiparallel spin 3d holes in conductivity. It is shown that in 2.2 at.% annealed Ti alloys ordering promotes 3d electron localization.

Abstract: Ultrasonic impact treatment (UIT) is a remarkable post-weld treatment, which reduce not only in external stress concentration, but also in residual stress in a welded joints. Internal and surface stresses were investigated on UIT treated welded joints by neutron and X-ray diffraction method. This paper discuses the effect of internal and surface residual stress and surface stress concentration after UIT on fatigue resistance by the comparison of fatigue experiments to predictions calculated with the results of the experimental investigations.

Abstract: The ORIGEN-S and ORIGEN2 codes were described in this paper, which were used to calculate the source term in the reactor core. The differences between ORIGEN-S and ORIGEN2 codes were compared and analyzed. The most significant difference was the methodology used to prepare and provide the neutron data for the codes, which directly affected the accuracy of calculation results of the ORIGEN2 code under different values of the parameters. Finally, the radioactivity of the actinide and fission products was calculated by changing the fuel enrichment, burnup and specific power of PWR, which was used to make quantitative analysis of the difference of results calculated by ORIGEN-S and ORIGEN2 and verify the degree of influence of various parameters on the results.

Abstract: Recent status of the technical development of the Bragg-edge neutron transmission imaging and its application to material science is presented. The neutron Bragg imaging has the advantages in measuring large area with reasonable spatial resolution, and it is a non-destructive method capable of looking inside a bulk material. Therefore, various information that are quite different from EBSD, synchrotron microtomography and X-ray/neutron scattering can be obtained by this method. We carried out quantitative imaging to obtain crystalline microstructural information in ultralow-carbon steels that received the high pressure torsion (HPT). The real-space distributions of texture and grain/crystallite size of HPTed steels of four torsion numbers were quantitatively visualized at once. As a result, we could deduce unique distributions of microstructural information depending on each torsion number, and correlated them with real-space distributions of the Vickers hardness. We also successfully developed a versatile strain tomography technique that can obtain tensor values for strain although traditional CT techniques can deal with only scalar values. The new CT algorithm, the tensor CT method, is based on our original algorithm called FBP-EM. The strain tensor tomography using FBP-EM was successfully applied for the experimental measured result obtained with the VAMAS neutron strain analysis international standard sample.