...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Diamond and Related Materials >Structural analysis of diamond mosaic crystals for neutron monochromators using synchrotron radiation
【24h】

Structural analysis of diamond mosaic crystals for neutron monochromators using synchrotron radiation

机译：中子单色器用同步加速器辐射的金刚石镶嵌晶体的结构分析

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The beams extracted from thermal neutron sources such as nuclear reactors are monochromatised by Bragg diffraction using imperfect single crystals with an angular mosaic spread of typically 0.2-0.8°. For neutron wavelengths below 1.5 A, the highest reflectivity of all crystalline materials is expected for diamond. Nowadays diamond single crystals with an appropriate mosaic spread exceeding a thickness of 1 mm can be grown by heteroepitaxy on an Ir/yttria-stabilised zirconia bilayer deposited on a Si(001) single crystal. To explain the observed neutron reflectivity being below the theoretically expected value, we have studied the spatial distribution of the mosaic structure of two crystals by high resolution X-ray diffraction using a laboratory X-ray source and synchrotron radiation. The first sample (A) showed a uniform mosaic spread of 0.18° ± 0.02° across the 1 cm wide sample. The peak shift of the X-ray rocking curves of 0.08° indicated a weak curvature of the crystal lattice. The measured absolute neutron peak reflectivity of 34% corresponded to 90% of the value predicted by theory. The peak width of the neutron rocking curve for the second sample (B) was twice as big, but here the peak reflectivity of 13% corresponded to only half of the theoretical value. This unfavourable behaviour could be assigned to a substantial spatial variation of the mosaic spread deduced from the synchrotron X-ray studies. X-ray diffraction with high spatial resolution indicated a mosaic block size below 50 μm for sample A. This was consistent with chemical etching experiments on the surface of a comparable sample which showed both randomly distributed dislocations and others that are arranged in boundaries of several 10 μm large domains.
机译：从热中子源（例如核反应堆）提取的光束通过布拉格衍射使用不完美的单晶进行单色化，其单晶马赛克的角度通常为0.2-0.8°。对于低于1.5 A的中子波长，钻石的所有晶体材料的反射率最高。如今，可以通过异质外延在沉积在Si（001）单晶上的Ir /氧化钇稳定的氧化锆双层膜上生长具有适当镶嵌分布且厚度超过1 mm的金刚石单晶。为了解释观察到的中子反射率低于理论期望值，我们使用实验室X射线源和同步加速器辐射，通过高分辨率X射线衍射研究了两种晶体的镶嵌结构的空间分布。第一个样品（A）在1厘米宽的样品上显示出0.18°±0.02°的均匀镶嵌分布。 X射线摇摆曲线的峰值偏移为0.08°，表明晶格曲率较弱。测得的绝对中子峰反射率为34％，对应于理论预测值的90％。第二个样品（B）的中子摇摆曲线的峰宽是原来的两倍，但此处的13％峰反射率仅相当于理论值的一半。这种不利的行为可以归因于从同步加速器X射线研究得出的镶嵌展布的实质性空间变化。具有高空间分辨率的X射线衍射表明，样品A的镶嵌块尺寸小于50μm。这与可比样品表面的化学蚀刻实验一致，该实验显示出随机分布的位错和其他分布在数十个边界内的位错μm大域。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号