Papers by Keyword: Neutron

Abstract: National Nuclear Energy Agency of Indonesia has several neutron beam instruments for materials science research. One of the instrument is Four Circle Diffractometer / Texture Diffractometer for study of crystal structure and texture measurement. Due to the instrument is fully occupied by many samples, the instruments has to be further developed in order to conduct experiment effectively and efficiently. For that reason, the instrument controller has been replaced with a new programmable controller that can handle all axis simultaneously. Since the controller has been replaced with the new one, a software for data acquisition and measurement also has been modified using a visual basic of programming language with an addition of function, i.e. an automatic measurement for either single-crystal or poly-crystal sample. The software calculates four peaks of Miller indices of the sample for determining the crystal position to be scanned. Then, the software performs the automatic measurement started from scanning the axis of θ-2θ, calculating the peak position by fitting the data obtained from sample diffraction data, then positioning the θ and 2θ axis to the peak position. Finally, the software performs the scanning of the π-χ axis for texture analysis, and save the experiment data into a certain format for the texture analysis software, i.e. Material Analysis Using Diffraction (MAUD).

Abstract: Measurements of internal strains in the superconducting constituent (Nb₃Sn phase in Nb₃Sn strand) in two cable-in-conduit conductors (CICC) for International Thermonuclear Experimental Reactor were performed using an engineering materials diffractometer TAKUMI of J-PARC. From strain measurements in a CICC for the toroidal field magnet after a performance test of cyclic current, in 100 mm long cut bars, a peak broadening and a large relaxation on residual strain were observed in Nb₃Sn phase at a portion received a high magnetic field (high field zone). Internal strain measurements were also conducted in a CICC for the central solenoidal magnets after the similar performance test, in the full-size shape as used in the performance test (3.6 m long) and in 100 mm long cut bars. Three main results were obtained. (1) Residual strain difference before and after the cutting to 100 mm long bar was about 0.1%, (2) a large relaxation on residual thermal strain was observed at the high field zone, and (3) the large relaxation on residual thermal strain at the high field zone was found mainly in a cross sectional side where the Lorentz force coming in.

Abstract: We tried to combine the basic principle of grammatical evolution with vortex-ring-fractal structures of atoms to create new molecule structures. This approach combines knowledge of evolutionary optimization with physical chemistry.

Abstract: Internal residual stresses in the pistons of motor vehicle engines were measured to verify the accuracy of residual stresses estimated by thermal simulations. Coarse crystal grains in aluminum casting alloys frequently make it difficult to measure neutron diffraction profiles if a conventional diffractometer is used for steady reactors [1]. Therefore, the Takumi diffractometer installed at the Japan Proton Accelerator Research Complex (J-PARC), which is a pulse neutron source, was applied to measure them. Residual stresses in pistons determined by the method of neutron diffraction were in good agreement with those estimated through thermal simulations. We concluded from these results that the thermal simulations could be applied to designing and producing pistons. Moreover, Young's modulus and Poisson's ratio for aluminum-silicon casting alloy were determined by using neutron diffraction. We also verified that internal residual stresses could be measured with a tensile sample holder by using the Takumi diffractometer.

Abstract: Peridotite containing high crystal water is used as concrete aggregates in this research. The mineral composition and thermal stability of peridotite are experimentally analyzed, and the concrete mix proportion design is optimized. The neutron shielding performance of peridotite concrete specimens are tested using ²⁴¹Am-Be neutron source. The transmission data of different thickness and different energy neutron are calculated. It concludes that peridotite concrete has a good performance in neutron shielding and peridotite is an excellent neutron shielding material.

Abstract: The effects of aqueous delithiation of lithium cobalt oxide crystals on the crystal texture and etching patterns has been studied by electron microscopy, x-ray and neutron diffraction at high resolution. The delithiation proceeds to exfoliation and in the process textural patterns that appear have been associated with periodic strains in the crystals developed by the delithiation.

Abstract: Focusing neutron beam with wide wavelength range is an indispensable technique used to compensate for weak signals from tiny samples in various experiments using pulsed neutron beam generated from high intensity proton accelerator facilities, such as J-PARC. Aspherical supermirror device is one of the most effective optical devices for focusing neutron beam with wide wavelength range since it has no chromatic aberration. Stack of aspherical supermirror enables us to focus neutron beams with wide divergence. Thin mirrors with a millimeter thickness are required to minimize the absorption loss of incident neutron beams since the thickness of a mirror shadows the reflective area of the other mirrors. Previously, we developed a fabrication process of a precise millimeter-thick elliptical supermirror. This process consists of noncontact figuring by the numerically controlled local wet etching technique, the finishing of surface without degrading mirror shape by low-pressure polishing, and the ion beam sputter deposition of NiC/Ti multilayers on both sides of the mirror substrate to compensate for film stress. In this paper, we report fabrication of elliptical supermirror with a thickness of 1 mm and development of multiply-arranged neutron focusing mirror device using stacked 4 fabricated elliptical supermirror with a thickness of 1mm.

Abstract: Cement-based material samples having 0%, 5%, 10% and 20% B₄C concentrations have been prepared for this reserach. Neutron attenuation measurement has been done by using 14.8MeV neutrons from the 5SDH-2 accelerator, and some mechanics properties of the same proportion also have been tested. It has been shown that when the B₄C precentage and thickness of the samples increase, neutron attenuation values of the samples increase. Both the flexural and compressive strength firstly increased with B₄C addition up to 10% approximately, and then decreased sharply with an addition up to 20%. It is thus possible to enhance the neutron shielding property of cement-based materials by adding B₄C.

Abstract: Keywords: Boron carbide, concrete, shielding, neutron, attenuation. Abstract. Boron carbide (B4C) is a ceramic material which is effectively absorb thermal neutron due to wide neutron absorption cross section. In this work, B4C is added into concrete as fine aggregates to test the attenuation properties by getting the attenuation coefficient of the concrete/ B4C. The samples of concrete/ B4C were exposing to the thermal neutron radiation source (241-Americium-Berylium) at the dose rate of 29.08 mR/h. The result show that the attenuation coefficient of the sample with 20wt% B4C is 0.299 cm-1 and the sample without B4C is 0.238 cm-1 and hence, concrete/ B4C is suitable as a shielded for thermal neutron radiation.

Abstract: Aspherical supermirrors are some of the most useful neutron-focusing optics. We aim to develop multiple aspherical supermirror devices using high-precision figured aspherical focusing supermirrors to focus neutron beams with high intensities, because multiple mirrors collect a very large beam divergence. Thin mirrors with millimetre thickness are required to minimize the absorption loss of incident neutron beams since the thickness of a mirror shadows the reflective area of other mirrors. However, it is difficult to fabricate thin mirror substrates with a form accuracy at the sub-micrometre level by conventional machining. Conventional machining deforms a substrate by machining force and spring back after machining causes figure error. Furthermore the deposition of supermirrors deforms the mirror substrate by film stress. Thus, we developed a new process of fabricating a precise millimetre-thick elliptical supermirror. This process consists of non-contact figuring by the numerically controlled local wet etching technique, the minimization of surface roughness without degrading form accuracy by low-pressure polishing with a polishing pressure less than about 7 kPa (1psi), and the ion beam sputter deposition of NiC/Ti multilayers on both sides of the mirror substrate to compensate for film stress. In this paper, we report on the fabrication results of aplano-elliptical mirror substrate with a thickness of 1 mm.