Journal Article Construction of a surface positronium lifetime spectroscopy apparatus with a spin-polarized low energy positron beam

前川, 雅樹  ,  和田, 健  ,  宮下, 敦巳  ,  河裾, 厚男

791 ( 1 )  , pp.012009-1 - 012009-5 , 2017-02 , IOP publishing
Description
For the study of surface magnetic phenomena using the spin-polarized positron annihilation method, we developed a surface positronium (Ps) lifetime spectrometer. A spin-polarized slow positron beam is generated by a sodium-22 source and a solid Krypton moderator and transported to the sample chamber by electrostatic lenses. Incident energy is adjusted by a retarding potential using a deceleration tube. For the lifetime measurement, the start signal is obtained from a secondary-electron detector installed in front of the sample. The stop signal is detected by a scintillation detector for annihilation gamma ray. As the performance test, Ps lifetime measurements were carried out and clear decay curves derived from ortho-Ps self-annihilation were successfully observed. This system might be used for the estimation of the spin polarization at the surface of the ferromagnetic materials.

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