| Project/Area Number |
12490006
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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 | 一般 |
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| Research Field |
広領域
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| Research Institution | The University of Tokyo |
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Principal Investigator |
HYODO Toshio The University of Tokyo, Graduate School of Arts and Sciences, Professor, 大学院・総合文化研究科, 教授 (90012484)
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| Co-Investigator(Kenkyū-buntansha) |
SAITO Haruo The University of Tokyo, Graduate School of Arts and Sciences, Research Associate, 大学院・総合文化研究科, 助手 (60235059)
NAGASHIMA Yasuyuki The University of Tokyo, Graduate School of Arts and Sciences, Research Associate, 大学院・総合文化研究科, 助手 (60198322)
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| Project Period (FY) |
2000 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥12,800,000 (Direct Cost: ¥12,800,000)
Fiscal Year 2001: ¥4,600,000 (Direct Cost: ¥4,600,000)
Fiscal Year 2000: ¥8,200,000 (Direct Cost: ¥8,200,000)
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| Keywords | positron annihilation / positron beam / positron annihilation induced X-ray / characteristic X-ray / thin film / positron moderator / tungsten mesh / electro-polish |
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| Research Abstract |
In conventional Auger-electron spectroscopy and characteristic X-ray spectroscopy, particles with sufficient energy are incident on specimens to remove core electrons by collisional ionization. When positrons with the energy lower than the binding energy of the core electrons are incident on the specimens, core electrons are removed by matter-antimatter annihilation and not by collisional ionization. The Auger-electrons from this process have been detected and used to characterize the elemental content of solid surface. The purpose of this project is to detect the X-rays from this process.
A slow positron beam was incident on a specimen and emitted X-rays were detected. The beam was produced using a new positron moderator made with a stack of electro-polished tungsten meshes. The moderation efficiency was measured to be 7.5×10^<-4>. This value is higher than any other transmission moderators except for inert gas solids. This moderator has the advantages over the inert gas solids that the treatment is easier, the cost is lower, and the long term stability is higher.
The yield of the X-rays is considerably low because the probability of creation of inner core holes by positron annihilation is small. Therefore, the background must be reduced sufficiently. There are two kinds of background : characteristic X-rays induced by the positron annihilation γ-rays and signals created by Compton scattering in the X-ray detector. Thin specimens are used to reduce the former background. A detector with thin Si (Li) crystal is developed to reduce the latter background. It is also reduced by the measurement under the condition where the γ-rays are not incident on the X-ray detector by coincidence measurements with a scintillation detector of the γ-rays.
However, we did not succeeded in detecting the X-rays in the term of the project.
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