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Effect of interfacial roughness correlation on diffuse scattering intensity in a neutron supermirror

界面粗さの相関が中性子スーパーミラーからの散漫散乱強度に与える影響

丸山 龍治; 山崎 大; 海老沢 徹*; 曽山 和彦

Maruyama, Ryuji; Yamazaki, Dai; Ebisawa, Toru*; Soyama, Kazuhiko

スーパーミラーを用いる中性子ビーム集光法は、反射における色収差がないのでJ-PARC等のパルス中性子源に適している。しかし、スーパーミラーからの反射ビームには入射角と反射角が等しくない散漫散乱成分が含まれる。NiC/Tiスーパーミラーからの散漫散乱強度はNi/Tiのそれよりも1桁以上小さく、集光素子への応用に適している。本研究では、Ni及びNiC膜の結晶構造とNi/Ti及びNiC/Ti多層膜の界面構造の解析を行い、スーパーミラーからの散漫散乱強度を抑えるには面内の相関長が小さく面間の相関長が大きい多層膜が有効であるという散漫散乱抑制のメカニズムを解明した。

Neutron supermirrors are one of the most useful multilayer devices in neutron experiments since a polychromatic neutron beam can be reflected. The diffuse intensity from a supermirror has to be suppressed since it causes a serious problem of low signal to background noise in focusing systems. The diffuse intensity can be decreased by more than an order of magnitude by adopting NiC/Ti multilayers instead of conventional Ni/Ti multilayers, which leads to a high performance focusing system with a diffuse intensity down to the order of 10$$^{-5}$$ of the specular intensity. In this study, in order to obtain the mechanism that controls the diffuse intensity from a supermirror, we investigated the crystal structure of Ni and NiC monolayers and the interface structure of Ni/Ti and NiC/Ti multilayers and demonstrated that a multilayer with a large vertical correlation length and a small lateral correlation length effectively suppresses the diffuse intensity from a supermirror.

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パーセンタイル:42.64

分野:Physics, Applied

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