1991 Fiscal Year Final Research Report Summary
Development of Positron Annihilation Life Time Detector with Emission of Ultraviolet Light.
| Project/Area Number |
01850146
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| Research Category |
Grant-in-Aid for Developmental Scientific Research
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| Allocation Type | Single-year Grants |
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| Research Field |
Physical properties of metals
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| Research Institution | Mie University |
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Principal Investigator |
SUZUKI Yasuyuki Mie University, Mechanical Engineering, Associate Professor, 工学部, 助教授 (80150283)
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| Co-Investigator(Kenkyū-buntansha) |
SANOO Masafumi Mie University, Mechanical Engineering, Professor, 工学部, 教授 (40023147)
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| Project Period (FY) |
1989 – 1991
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| Keywords | Positron annihilation / Life time Measurement / gamma ray detector / Emission of ultra-violet light / Time resolution / positron / Life time |
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| Research Abstract |
Measurement by using a positron, which is an anti-particle of an electron is focused as research method for developing of semiconductors or new materials, by a researcher who is not a specialist of positron measurement. It becomes a popular method as measurement of crystalline defects or distribution of electron density. Especially life time (LT) measurement is very useful as non-destructive testing of crystalline defects. A positron injected by beta pulse decay of 22 sodium and a gamma ray of 1.28 mega-electron volt (MeV) is emitted at the same time. The injected positron is trapped by crystalline defects. It annihilates with an electron and they emitted two gamma rays of 0.51 MeV. Probability of annihilation is proportional to electron density at defects. If we measure time difference between two gamma rays (l. 28Mev and 0.51 MeV), We obtain electron density and quantity of defects as life time and intensity respectively. As the resolution of life time is required 200 pico second, the measurement system is required special electronics. And as gamma rays are emitted with same probability for all direction, it needs to set up detector to sample as near as possible. So we need development of a smaller detector with good time resolution.
On this research, we use barium di-flouride as a scintillator detecting gamma rays and R1893 with Hamamatsu Photonics Co. as a photo-multiplier. We developed a small detector whose diameter is 15 mm. When we measure a gamma ray of 0.51 MeV by this detector, we obtain output pulse from anode, which rise time is 0.8 nano second and pulse height is 250 mV. Full width half mean is 210 pico second. We obtained almost same specification as normal C31024 of RCA Co. A diameter of this detector is one-third as small as the normal detector. It will be useful for future posittron measurement at high temperature or ultra-low temperature.
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