放射光による極微小単結晶の構造解析法の開発

在材料科学领域，长期以来，人们一直希望开发设备来获取微米级结晶物质的结晶学信息，例如从地球或陨石获得的非常微小的矿物。同步辐射(SR)可以很好地处理这么小的样品，因为它的强度很高。即使在SR的情况下，也应该特别注意测量非常弱的衍射强度。在不使用SR的情况下，50微米的尺寸可能是衍射法检查的样品的极限。衍射光强与样品的体积成正比，微米级晶体的衍射光强估计为上述极限的10-5倍。因此，实验的噪音水平应该尽可能低。如果噪声水平变得可以忽略不计，则可以通过调整测量时间将信号持续累积到所需的强度水平。为此，实验应在真空中用静止结晶法和非常窄的准直X射线光束进行。由于上述原因，以及通过倒易空间原点的倒排上每个布拉格反射的强度相互叠加，从而使照相底片上的一个衍射点加强的事实，采用了劳厄方法。劳厄相机安装在光子工厂的BL-4B(距离光源20米)，密封在真空中，安装在非常窄的准直器中。该系统的研制达到了在环流为128~125 mA的条件下，直径0.8微米的钼单晶在成像板上进行50分钟多次布拉格反射的水平。得到的Laue照片与计算的图样吻合较好。

In the field of material sciences, it has long been desired for developing the equipment to obtain crystallographic information of micrometer-size crystalline substances such as very minute minerals obtained from earth or meteorites. Synchrotron radiation(SR) could be a candi-date to deal with such a small specimen because of its high intensity.Even in the case of SR, special care should be paid for the measurement of very weak diffracted intensities. In the case not using SR, the size of fifty micrometers might be the limit for the specimen to be examined by diffraction method. The diffracted intensity is proportional to the volume of specimen, and that of micrometer sized crystal is estimated as 10^<-5> times of that of the limit mentioned above. The noise level of the experiment, therefore, should be as low as possible. If the noise level becomes negligibly small, the signal could be accumulated continually to the desired intensity level by adjusting measuring time. The experiment,for the purpose, should be carried out in vacuum with stationary crystal method and with very narrow collimated X-ray beam.The Laue method is employed by the above reason as well as the fact that the intensitiy of each Bragg reflection on a reciprocal row passing through the origin of the reciprocal space is superposed with each other, which also intensifies a diffraction spot on the photographic plate.The Laue camera is set up at BL-4B (located at 20 m from source point) of Photon Factory, sealed in vacuum and installed in very narrow collimater. The development of the system has been performed to the level at which several Bragg reflections of molybdenum single crystal with 0.8 micrometer in its diameter can be taken on the imaging plate for fifty minutes ex-posure with ring current from 128 to 125 mA. The obtained Laue photograph is found to be in good agreement with the calculated pattern.