| Project/Area Number |
09440140
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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 |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | Osaka City University |
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Principal Investigator |
HATA Thoru Osaka City University, Faculty of Science, Professor, 理学部, 教授 (10156333)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUBARA Akira Osaka City University, Faculty of Science, Research Associate, 理学部, 助手 (00229519)
ISHIKAWA Osamu Osaka City University, Faculty of Science, Associate Professor, 理学部, 助教授 (90184473)
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| Project Period (FY) |
1997 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥14,400,000 (Direct Cost: ¥14,400,000)
Fiscal Year 1999: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1998: ¥4,200,000 (Direct Cost: ¥4,200,000)
Fiscal Year 1997: ¥8,500,000 (Direct Cost: ¥8,500,000)
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| Keywords | helium 3-4 mixture / superfluidity / nuclear demagnetization / thermal boundary resistance / viscosity / ultralow temperature / fine platinum powder / heat exchanger |
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| Research Abstract |
The final goal of this research is to discover a superfluidity of helium 3 quasiparticles in helium 3-4 liquid mixtures at ultra-low temperatures below 100 μK.It is very difficult to cool helium 3-4 mixtures compared with pure helium 3 liquid, because there exists large thermal resistance, called Kapitza resistance, between heat exchangers and helium 3-4 liquid mixtures. In this research, we tried to find the optimum condition witlt computing cooling simulation of the mixtures based on our former experiments improving below items : 1. To make more efficient nuclear stages in a double nuclear demagnetization., 2. To use ultra-fine platinum powder as a heat exchanger, which has larger surface area.3. To make a sample cells without plastics like Stycast.
It was found that the efficiency of the refrigerator was leveled up by one order higher using 8T+15T magnets instead of 6T+8T.We also managed to make ultra-fine platinum powder with a huge surface area of 33 m2/g.. We could decrease the total amount of heat release from plastics which has a similar behavior to heat leak from outside. Our simulation of cooling shows that we can cool helium 3-4 liquid mixtures down to 50 μK.we also developed the new type of a sensor made of silicon single crystal to detect the viscosity. If ultra-fine platinum powder contains a large amount of hydrogen, large heat generation due to the ortho-para conversion might be expected. It is found that our platinum powder contains more than 1000 ppm of hydrogen, and the hydrogen can be removed by heating up above 500 ℃ in vacuum.
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