Development of X-ray Acoustic Spectrometer Using Synchrotron Radiation

利用同步辐射x射线源研制了本课课组创新的x射线声谱仪（XAS）。研制了一种利用驻极体的x射线声探测器（XA cell）。x射线斩波器、第一离子室、XA细胞和第二离子室在光学台上依次排列。将XA细胞安装在X-Z脉冲级上，对样品进行二维扫描成像。该级的扫描、锁相放大器和两个皮安计的数据采集由微机通过GP-IB线进行调节。最后组装并建立了可自动运行的XAS整体系统。为了提高灵敏度，我们还开发了一种新的探测器，它可以光学地探测振动膜的运动，我们称之为“光学麦克风”。另一种新的检测方法是利用光电传感器PVDF聚合物薄膜，该方法同样灵敏，可以在真空下使用。方法的发展这种方法在材料的非破坏性地下评价能力方面是独一无二的。为此，x射线被调制成半脉冲形状并照射到样品上。结果表明，延迟信号成分来源于地下物质。通过x射线束扫描，揭示了材料在表面下的分布。我们称这种方法为“半脉冲XAS法”。XA-EXAFS光谱和聚焦x射线成像也被成功地应用于各种模型样品中，以寻找原子结构分析和材料三维无损评价的潜力。

Apparatus and methods for X-ray Acoustic Spectroscopy (XAS) which was innovated by our research group were developed using synchrotron radiation X-ray source.1.Development of ApparatusAn X-ray acoustic (XA) detector (XA cell) using a electret was developed. X-ray chopper, 1st ion chamber, this XA cell and 2nd ion chamber were aligned in sequence on a optical stage. The XA cell was mounted on the X-Z pulse-stage in order to get the 2 dimensional scanning of the sample for imaging. The scanning of this stage and data acquisition from a lock-in amplifier and the two pico-ampere meters were regulated by a microcomputer using GP-IB bas line. A total system for XAS which can be operated automatically was finally assembled and established.A new detector which detects the movement of a vibrating membrane optically, we call "optical microphone" was also developed for more sensitivity. One more new detection method using a photopyroelectric sensor, PVDF polymer film, was successfully developed which is also sensitive and can be used under vacuum.2.Development of MethodologyThis method is unique in the ability of non-destructive sub-surface evaluation of materials. For this purpose, X-ray was modulated in semi-pulse shape and irradiated on to the samples. It was found that the delayed signal components was originated from a sub-surface material. By scanning of X-ray beam, the distribution of materials under the surface was revealed. We call this method as "Semi-Pulse XAS method". XA-EXAFS spectroscopy and XA-imaging using focused X-ray beam were also developed and applied successfully to various model samples to find the potentials for analysis of atomic structure and 3-dimensional non-destructive evaluation of materials.