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Hirade, Tetsuya
no journal, ,
Positronium (Ps) creates a bubble in liquids because of a negative work function and the ortho-Ps annihilation probability depends on the size of the bubble. The oscillation of the ortho-Ps annihilation probability at very young positron ages, i.e. before 1ns, was successfully observed in room temperature ionic liquids (RTILs). The frequency of the oscillation deceased just above the melting point. Moreover, the stable annihilation rates at older positron ages in RTILs are much smaller than the annihilation rates of other liquids having similar surface tensions, and the rates do not become smaller at higher temperatures. These phenomena are probably caused by the complicated RTIL structure.
Fukaya, Yuki
no journal, ,
no abstracts in English
Maekawa, Masaki; Li, H.; Kawasuso, Atsuo
no journal, ,
Jiang, L.*; O'Rourke, B. E.*; Harada, Yoshihisa*; Takatsu, Shuhei*; Ito, Kenji*; Okubo, Masataka*; Hirade, Tetsuya; Uedono, Akira*; Suzuki, Ryoichi*; Takai, Kenichi*; et al.
no journal, ,
We are studying the depth dependence of the density of the defects induced by the electrical discharge machining (EDM) in SUS316L, using the electron probe microanalysis (EPMA), Positron annihilation lifetime spectroscopy (PALS) and X-ray diffraction (XRD). EPMA results show a large change in the composition over the first 10 
m. This layer can be assumed to correspond to the recast layer. PALS and XRD results suggest a defect layer with a thickness of around 50 m. This depth can be assumed to correspond to the heat affected zone where dislocations and vacancy clusters exists. For PALS (and other methods) analysis, it is recommended to remove the topmost 100 m of the samples by chemical polishing after EDM.