1991 Fiscal Year Final Research Report Summary
Studies on Lattice Defects in Solid Helium by SR X-Ray Topography.
| Project/Area Number |
63060002
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| Research Category |
Grant-in-Aid for Specially Promoted Research
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| Allocation Type | Single-year Grants |
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| Research Institution | Tokyo Engineering University |
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Principal Investigator |
SUZUKI Hideji Tokyo Engineering University, Professor., 工学部, 教授 (00011411)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAJIMA Tetsuo National Laboratory for High Energy Physics, Photon Factory, Associate Professor, 放射光実験施設, 助教授 (20005888)
SUZUKI Takayoshi University of Tokyo, Institute of Industrial science, Professor, 生産技術研究所, 教授 (70013208)
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| Project Period (FY) |
1988 – 1991
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| Keywords | HCP ^4He / BCC ^3He / X-ray topography / Subboundary / \Martensitic transformation / Climb motion / Dilution refrigerator |
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| Research Abstract |
There is no work on X-ray topography of solid helium other than our project. Therefore we must develop the method of the research and to build equipments for the research. Namely, we must reduce the heating of the sample chamber by the irradiation of X-rays at ultra low temperatures so that the temperature of the sample during the experiment is sufficiently lower than the melting point of ^3He. We must prepare a sample chamber for high pressure solid helium with wide area of windows for X-rays, an equipment to rotate the sample chamber at ultra low temperatures around a horizontal and a vertical axes. We must also build an automatic recording system of X-ray topographs on nuclear plates to observe the change in configurations of lattice defects continuously. We expected to complete the new equipments during the first and second years, but the sample chamber and its rotating system must be produced by ourselves and extra six months were spent. This delay could not be recovered during th
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e later period of the project. We demonstrated that it is possible to rotate the sample chamber at ultra low temperatures around two axes without heating more than 0.1 K. The dilution refrigerator has a large heat load of the rotating system of the sample chamber, which also increases heat leak to the sample chamber. Then the lowest temperature of sample chamber was 0.2 K.
Under the above-mentioned conditions we observed the process of crystal growth and annealing process of hcp ^4He and bcc ^3He. It was found that there is significant difference between hcp ^4He and bcc ^3He in the formation of subboundaries. This difference is interpreted on the basis of the large differences of the rate of climb motion of dislocations in hcp and bcc crystals. Namely, the dislocations in basal plane of the hcp crystal extends widely and the climb rate is negligibly small, while dislocations in the bcc crystal is hardly extend and the climb motion is quite easy. This interpretation is also applied to the marked subboundaries formed after the martensitic transformation of hcp^4 He into the bec structure.
The dynamical effect of diffraction is negligible in solid helium. Therefore, we simulated the contrast of dislocation image based on the kinematical theory of diffraction. The result is denoted that the reflection from the core material of dislocation with a diameter of about 1mum disappears. This result of simulation seems to agree with the observed results. Less
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