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明午 伸一郎; 大井 元貴; 池崎 清美*; 川崎 智之; 木下 秀孝; 圷 敦*; 西川 雅章*; 福田 真平
Proceedings of 12th International Topical Meeting on Nuclear Applications of Accelerators (AccApp '15), p.255 - 260, 2016/00
At the J-PARC, spallation neutron and muon sources has built at placed at the MLF by using 3-GeVproton beam. By the result of post irradiation examination of the mercury target vessel, damage was found on the surface of the vessel due to the pitting erosion caused by the proton beam. Since the pitting erosion is known to be proportional to the 4th power of the beam current density, peak current density should be kept as low as possible so that beam-flattening system by nonlinear beam optics using octupole magnets was developed. For efficiently beam tuning, a tool was developed by using SAD code system. By the result of the beam study, the peak current density at the target can be reduced by 30% with the present nonlinear optics.
福田 秀孝*; Y.Janssen*; 藤井 博信*; 浴野 稔一*; 森井 幸生
Journal of the Magnetics Society of Japan, 23(1-2), p.108 - 110, 1999/00
CeFeは斜方面体構造をとる2-17型希土類鉄化合物のうちでは唯一、T=210K以下で反強磁性を示す。中性子回折実験の結果、210Kから110Kの間ではFe部分格子のC面内にある磁気モーメントが、波数ベクトルQ=0.0372でC軸方向に伝播するらせんスピン構造をとること、110K以下ではC軸方向に二倍の超格子磁気セルを持ち、波数ベクトルQ=0.0435でC軸方向に伝播する変調らせんスピン構造をとることが判明した。伝導実験からは、110K以下で巨大磁気抵抗効果が観測された。一方LuFeには巨大磁気抵抗効果は見いだせない。