1999 Fiscal Year Final Research Report Summary
Construction of a desk-top-sized and mobile positron lifetime spectrometer with β^<+->γ coincidence and positron energy selection for in-situ studies of lattice defects
| Project/Area Number |
10555212
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
Physical properties of metals
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| Research Institution | Osaka University |
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Principal Investigator |
SHIRAI Yasuharu Department of Materials Science and Engineering, Osaka University, Professor, 大学院・工学研究科, 教授 (20154354)
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| Co-Investigator(Kenkyū-buntansha) |
ARAKI Hideki Department of Materials Science and Engineering, Osaka University, Associate Professor, 大学院・工学研究科, 助教授 (20202749)
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| Project Period (FY) |
1998 – 1999
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| Keywords | positron beam / positron lifetime / β^<+->γ coincidence / lattice defect / non-destructive testing |
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| Research Abstract |
The positron lifetime measurement is a non-destructive method for sensitively detecting and differentiating crystal lattice defects with size of nanometer order in materials. In the conventional positron lifetime measurement it is necessary to sandwich a positron source between two identical pieces of sample material, because all positrons emitted in all directions from the positron source have to annihilate with electrons in the sample material. It is therefore quite difficult to measure positron lifetime in the place where the sample exists, without cutting two pieces out of the sample material.
We have constructed a new β^<+->γ coincidence lifetime spectrometer with positron energy selection in order to achieve in-situ measurement of positron lifetime. In the spectrometer a positron source is placed well apart from the sample. The positrons emitted from the positron source are selected in energy by a magnetic lens and only the positrons with a certain energy are led to an advanced photo diode. When the positron passes through the diode, it gives a start signal to the coincidence circuit. The positron that passed through the positron detector is again focused on the sample by a magnetic lens. The positron annihilates with an electron in the sample. The annihilation photon is detected to use as a stop signal. The new positron lifetime spectrometer with fast positron beam is desk-top-sized and can be easily carried.
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