Studies on Lattice Defects in Solid Helium by SR X-Ray Topography.

通过 SR X 射线形貌术研究固体氦中的晶格缺陷。

• 批准号: 63060002
• 负责人: SUZUKI Hideji
• 金额: $ 99.84万
• 依托单位: Tokyo Engineering University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Specially Promoted Research
• 财政年份: 1988
• 资助国家: 日本
• 起止时间: 1988 至 1991
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-63060002/
• 关键词: HCP ^4He; BCC ^3He; X-ray topography; Subboundary; \Martensitic transformation; Climb motion; Dilution refrigerator; 結晶成長; 内部応力; サブ・バウンダリ; 拡張転位; 固体ヘリウム; 転位; X線トポグラフィ; 像のコントラスト; 格子欠陥; 共焦点型レーザー顕微鏡; カーボン繊維強化プラスチック

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 … More 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

除了我们的项目之外，没有关于固体氦的X射线形貌的工作。因此，我们必须发展研究的方法和建立研究的设备。也就是说，我们必须减少超低温X射线照射对样品室的加热，使实验过程中样品的温度充分低于^3He的熔点。我们必须准备一个高压固体氦的样品室，该样品室具有用于X射线的大面积窗口，一个在超低温下围绕水平轴和垂直轴旋转样品室的设备。我们还必须建立一个核板X射线形貌自动记录系统，以连续观察晶格缺陷的组态变化。我们原计划在第一年和第二年完成新设备，但样品室及其旋转系统必须自行生产，多花了六个月的时间。此延迟无法在 ...更多信息 项目后期。我们证明了在超低温下围绕两个轴旋转样品室而不加热超过0.1 K是可能的。稀释制冷机具有样品室的旋转系统的大的热负荷，这也增加了到样品室的热泄漏。在上述条件下，我们观察了hcp ^4He和bcc ^3He的晶体生长过程和退火过程。发现hcp ^4He和bcc ^3He在亚界面的形成上有明显的差别。这种差异是根据六方晶系和体心立方晶系位错攀移速率的巨大差异来解释的。也就是说，六方晶系的位错在基面上扩展很广，攀移速率很小，而体心立方晶系的位错几乎不扩展，攀移运动很容易。这一解释也适用于hcp^4 He马氏体相变为bec结构后形成的显著亚晶界，在固态氦中衍射的动力学效应可以忽略不计。因此，我们根据运动学衍射理论模拟了位错像的反差。结果表明，直径约为1 μ m的位错从芯材的反射消失。这一模拟结果似乎与观测结果一致。少

项目成果

T.Nakajima: Rev.Sci.Inst.(1988)

T.Nakajima：Rev.Sci.Inst.(1988)