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

除了我们的项目外，没有其他关于固体氦的x射线形貌的工作。因此，必须发展研究方法和研究设备。也就是说，我们必须在超低温下通过x射线照射来减少样品室的加热，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，有宽面积的x射线窗口，一个在超低温度下绕水平轴和垂直轴旋转样品室的设备。我们还必须在核板上建立x射线地形图的自动记录系统，以连续观察晶格缺陷的构型变化。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由我们自己制作，并额外花费了6个月的时间。这种延迟在项目的后期无法恢复。。我们证明了在不加热超过0.1 K的情况下，可以在超低温下围绕两个轴旋转样品室。稀释制冷机样品室旋转系统的热负荷较大，也增加了样品室的热泄漏。样品室最低温度为0.2 K。在上述条件下，观察了hcp ^4He和bcc ^3He的晶体生长过程和退火过程。发现hcp ^4He与bcc ^3He在亚界的形成上存在显著差异。这种差异是基于hcp和bcc晶体中位错爬升运动速率的巨大差异来解释的。即hcp晶体基面位错扩展广泛，爬升速率小到可以忽略不计，而bcc晶体的位错几乎不扩展，爬升运动很容易。这一解释也适用于hcp^4 He向bec结构马氏体转变后形成的显著亚边界。在固体氦中，衍射的动力学影响可以忽略不计。因此，我们基于衍射的运动学理论，模拟了位错图像的对比。结果表明，直径约为1 μ m的位错对岩心材料的反射消失。这一模拟结果似乎与观测结果相吻合。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