Browsing by Author "Yamada, NL"

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    The performance of magnetic lens for focusing VCN-SANS
    (Elsevier, 2011-04-01) Yamada, M; Iwashita, Y; Kanaya, T; Ichikawa, M; Tongu, H; Kennedy, SJ; Shimizu, HM; Mishima, K; Yamada, NL; Hirota, K; Carpenter, JM; Lal, J; Andersen, KH; Geltenbort, P; Guerard, B; Manzin, G; Hino, M; Kitaguchi, M; Bleuel, M
    We have developed a prototype rotating-permanent magnet sextupole lens (named rot-PMSx) for more efficient experiments with neutron beams in time of flight (ToF) mode. This lens can modulate the focusing strength over range 1.5 x 10(4)T/m(2) <= g' <= 5.9 x 10(4) T/m(2). Synchronization between the modulation and the beam pulse produces a focused beam without significant chromatic aberration. We anticipate that this lens could be utilized in focusing small angle neutron scattering (SANS) instruments for novel approach to high resolution SANS. We carried out experiments testing the principle of this lens at the very cold neutron (VCN) beamline (PF2) at Institut Laue-Langevin (ILL), France. The focused beam image size at the detector was kept constant at the same beam size as the source (approximate to 3 mm) over a wavelength range of 30 angstrom <= lambda <= 48 angstrom in focal length of approximate to 1.14m. The flux gain was about 12 relative to a beam without focusing, and the depth of focus was quite large. These results show the good performance of this lens and the system. Thereupon we have demonstrated the performance of this test bed for high resolution focusing of VCN-SANS for a well-studied softmatter sample; a deuterium oxide solution of Pluronic F127, an (PEO)(100)(PPO)(65)(PEO)(100) tri-block copolymer in deuterium oxide. The results of the focusing experiment and the focusing VCN-SANS are presented. (C) 2010 Elsevier B.V. All rights reserved.
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    Time-resolved neutron reflectometry and photovoltaic device studies on sequentially deposited PCDTBT-fullerenel layers
    (ACS Publications, 2014-09) Clulow, AJ; Tao, C; Lee, KH; Velusamy, M; McEwan, JA; Shaw, PE; Yamada, NL; James, M; Burn, PL; Gentle, IR; Meredith, P
    We have used steady-state and time-resolved neutron reflectometry to study the diffusion of fullerene derivatives into the narrow optical gap polymer poly[N-9″-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) to explore the sequential processing of the donor and acceptor for the preparation of efficient organic solar cells. It was found that when [6,6]-phenyl-C61-butyric-acid-methyl-ester (60-PCBM) was deposited onto a thin film of PCDTBT from dichloromethane (DCM), a three-layer structure was formed that was stable below the glass-transition temperature of the polymer. When good solvents for the polymer were used in conjunction with DCM, both 60-PCBM and [6,6]-phenyl-C71-butyric-acid-methyl-ester (70-PCBM) were seen to form films that had a thick fullerene layer containing little polymer and a PCDTBT-rich layer near the interface with the substrate. Devices composed of films prepared by sequential deposition of the polymer and fullerene had efficiencies of up to 5.3%, with those based on 60-PCBM close to optimized bulk heterojunction (BHJ) cells processed in the conventional manner. Sequential deposition of pure components to form the active layer is attractive for large-area device fabrication, and the results demonstrate that this processing method can give efficient solar cells. © 2014, American Chemical Society.