A study of three-dimensional structures of interplanetary dust by imaging x-ray microtomography.

美国宇航局星尘任务收集的宇宙尘埃(行星际尘埃粒子和未熔融的微陨石)和彗星尘埃的三维结构在春季8号利用X射线显微层析成像技术进行了研究。本项目期末克服了X射线放大光学系统和样品旋转台的问题，利用衰减对比度进行层析成像，获得了空间分辨率小于100 nm的超高空间分辨率的三维结构。我们还对一些样品进行了空间分辨率约为0.5μm的投影CT检查，从宇宙尘埃样品的三维结构中获得了样品的物理性质，如孔隙率和密度。此外，还成功地获得了样品的分维。被认为来自彗星的宇宙尘埃的分维明显小于3，这可能是c…聚集的证据太阳系早期尘埃的组成粒子较多。作为星尘预审组成员之一的星尘样本分析揭示了气凝胶收集器中撞击轨迹和轨迹中终端颗粒的三维结构。这些结果提供了关于撞击过程的信息以及用于进一步详细破坏性分析的基本纹理信息。并结合红外天文观测，对宇宙尘埃矿物的红外光谱进行了实验研究，为宇宙尘埃的综合研究奠定了基础。此外，还在Spring8上研制了层析成像系统并对其性能进行了评估。定量计算CT图像的亮度。利用这个公式，我们建立了一种用减法绘制Fe和Cs的三维元素图的技术。这一结果适用于陨石和其他陆地样本以及宇宙尘埃样本。较少

Three-dimensional structures of cosmic dust (interplanetary dust particles and unmelted micrometeorites) and cometary dust that was collected by NASA Stardust mission were examined using x-ray microtomography at SPring-8. Three-dimensional structures with ultra-high spatial resolution of less than 100 nm has been obtained at the end of the term of this project by imaging tomography using attenuation contrast by overcoming troubles in an optical system for enlargement of x-ray beams and a sample rotation stage. We have also examined some samples by projection CT with the spatial resolution of about 0.5 μm. Physical properties of the samples, such as porosities and densities, were obtained from the three -dimensional structures of the cosmic dust samples. Furthermore, fractal dimensions of the samples were successfully obtained. The fractal dimensions of cosmic dust which was considered to be derived from comets are significantly less than 3. This may suggest evidence of aggregation of c … More onstituent particles of the dust in the early stage of the solar system. The Stardust sample analysis, which was performed as one of the members of preliminary examination team of Stardust, revealed the three-dimensional structures of impact tracks in aerogel collectors and terminal particles in the tracks. These results gave information about the impact processes as well as basic textural information for further detailed destructive analyses. Experimental studies of infrared spectrum of cosmic dust minerals in connection with infrared astronomical observation have been also made for comprehensive research on cosmic dust. Furthermore, development of the tomography system at SPring-8 and evaluation of its performance have been done. Brightness of CT images was quantitatively formulated. By using this formulation, we have established a technique for three-dimensional element mapping of Fe and Cs using the subtraction method. The results were applied to meteorites and other terrestrial samples as well as cosmic dust samples. Less