Neutron reflectometry is one of the powerful tools to investigate surface and interfacial structures of materials in the spatial range from nm to sub-μm. Because hydrogen and deuterium atoms have different scattering length for neutrons, this method can distinguish deuterated materials from normal ones in the mixture of soft-condensed matters, such as polymer blends, bio-mimic membranes, and so on. Furthermore, high transmissivity of neutrons to materials enables us to probe deeply-buried interfaces such as solid/liquid interfaces in a non-destructive way. In J-PARC, we have transferred an old reflectometer ARISA from the KENS facility in KEK Tsukuba campus to the BL16 beam port at J-PARC/MLF viewing a coupled liquid hydrogen moderator, and started to accept the neutron beam on a new reflectometer ARISA-II in December, 2008. Although the beam intensity of ARISA-II was about ten times more than that of ARISA, background was high because of frame overlap. In this summer, we have installed disk chopper as a tail cutter, mirror holder to control beam path, iron collimator and beam duct for background suppression. Thanks to the upgrades, S/N ratio is drastically improved and the observable reflectivity reaches 10-7.
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