A Neutron depolarization measurement of single crystal Fe by using a He neutron spin filter and magnetic super-mirrors

Okudaira, Takuya; Oku, Takayuki   ; Sakai, Kenji ; Hiroi, Kosuke  ; Shinohara, Takenao   ; Ino, Takashi*; Kira, Hiroshi*; Hayashida, Hirotoshi*; Suzuki, Junichi*; Kakurai, Kazuhisa*; Aizawa, Kazuya  

We have been developing a He neutron spin filter (NSF) for efficient utilization of pulsed neutrons at J-PARC MLF, since it can polarize neutrons effectively in a wide energy range. We performed demonstrative experiments using the He-NSF at small-angle scattering (BL15 TAIKAN), reflection (BL17 SHARAKU) and imaging instrument (BL22 RADEN) of J-PARC MLF, and got reasonable results. Then, we have performed a demonstrative study of polarized-neutron single-crystal diffraction measurement at BL18 (SENJU). The sample was a single crystal Fe. As the result, expected flipping ratios of Bragg beaks were not observed. Therefore, we have performed a depolarization experiment of neutrons transmitted through the sample, and found out neutron severe depolarization occurred in the sample which was almost magnetically saturated under an applied magnetic field of 4.2 k Gauss. In this paper, we will show the experimental results of the depolarization experiment of neutrons transmitted through the single crystal Fe and discuss them.