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

除了我们的项目外，还没有关于固体氦的X射线形貌的工作。因此，我们必须发展研究的方法，并为研究建立设备。也就是说，我们必须在超低温下通过X射线照射来降低样品室的加热，以使实验过程中样品的温度充分低于~3He的熔点。我们必须准备一个具有大面积X射线窗口的高压固体氦样品室，一个在超低温下绕水平和垂直轴旋转样品室的设备。我们还必须建立一个核板上X射线形貌图的自动记录系统，以连续观察晶格缺陷组态的变化。我们希望在第一年和第二年完成新的设备，但样品室及其旋转系统必须由我们自己生产，并额外花费了6个月的时间。此延迟在…期间无法恢复更多的是项目的后期。我们证明了样品腔在超低温下绕两个轴旋转是可能的，而加热不超过0.1K。稀释制冷机样品室旋转系统的热负荷很大，这也增加了样品室的热泄漏。在此条件下，我们观察了HCP、4He和体心立方3He的晶体生长和退火过程。结果表明，Hcp^4He和体心立方^3He在亚界的形成上存在显著差异。这种差异是基于位错在体心立方晶体和六方体心立方晶体中攀移运动速度的巨大差异来解释的。也就是说，hcp晶体的基面位错扩展很广，爬升速率可以忽略不计，而bcc晶体中的位错几乎没有扩展，爬升运动非常容易。这种解释也适用于hcp^4He马氏体相变到BEC结构后形成的明显亚界面，在固体氦中绕射的动力学效应可以忽略不计。因此，我们基于绕射运动学理论，对位错像的对比度进行了模拟。结果表明，直径约为1微米的位错核材料的反射消失。这一模拟结果似乎与观测结果相吻合。较少

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