Development of high-pressure topography and application to rheology of mantle minerals

1.高压X射线形貌术的发展：为了更好地了解晶体在压力作用下的塑性和相变，我们利用同步辐射和Kawai型多砧座高压装置，发展了原位高压X射线形貌术。将单晶样品放置在高压室中，用X射线CCD相机通过砧座缝隙观察晶体的衍射斑。虽然可见光斑受到胶块/WC砧座阴影的限制，而且长的样品到相机的距离使得光斑很难引导到相机，但我们可以在高压和温度条件下观察到光斑。2.晶体形貌图像的观测：利用该技术研究了石英、橄榄石和金红石单晶的形貌图像。在室温下初始压缩到几十吨的过程中，观察到斑点的加宽。在加热过程中，加宽的光斑恢复到原来的状态。恒温下的进一步压缩导致斑点显著加宽。回收的样品是多晶体的，可能是由于压力。虽然我们还需要进一步的技术发展，如应力控制，但这项技术对于观察晶体缺陷和单晶在压力和温度下的转变是非常有用的。

1.Development of high-pressure X-ray topography : To better understand crystal plasticity and phase transformation under pressure, we developed in-situ high-pressure X-ray topography technique using synchrotron radiation and Kawai-type multi-anvil high pressure device. Single crystal sample is placed in high pressure cell, and diffraction spots from the crystal are obseved using X-ray CCD camera, through anvil gaps. Although observable spots are limited by gude-blocks/WC anvil shadows and long sample-to-camera distance makes guiding spots to the camera very difficult, we could observe spots at high-pressure and temperature conditions.2.Observations of topographic images of crystal : Single crystals of quartz, olivine and rutile have been studied using this technique. During initial compression to few tens tons at room temperature, broadening of spots were observed. During heating, broadened spot reverted to original. Further compression under constant temperataure caused significant broadening of the spots. Recovered samples were polycrystalline, possibly due to stress. Athough we still need further technical developments such as stress control, this technique can be very useful to obsereve crystal defects and transformation of single crystals under pressure and temperature.