上海光源基于EPICS的QXAFS数据采集系统的研究与实现

发布时间：2018-01-20 16:21

本文关键词： 上海光源快速扫描X射线吸收精细结构双晶单色器实验物理与工业控制系统数据采集系统　出处：《中国科学院研究生院（上海应用物理研究所）》2015年博士论文　论文类型：学位论文

【摘要】：随着同步辐射光源的出现和发展，各种新的同步辐射实验方法不断涌现。发展新的同步辐射实验方法并利用它们开展对相关领域科学问题的研究已经成为同步辐射光源应用领域的一项重要内容。X射线吸收精细结构谱（X-ray Absorption Fine Structure，XAFS）是一种随着同步辐射光源的发展而逐渐成熟起来的强有力的结构分析方法。不同于普通XAFS实验方法所采用的“step-by-step”模式的数据采集方式，快速扫描X射线吸收精细结构谱（Quick-scanning X-rayAbsorption Fine Structure，QXAFS）实验方法采用“on-the-fly”的数据采集方式，能够在双晶单色器（Double Crystal Monochromator，DCM）连续运动的过程中获取实验样品的QXAFS谱。QXAFS实验方法可以在秒量级完成一个XAFS谱的数据采集工作，适合开展对催化工业、化学过程、生物传感和材料科学等领域的动态原位过程的研究。与能量色散XAFS（Energy-Dispersive X-rayAbsorption Fine Structure，EDXAFS）、泵浦-探测XAFS（pump-probe X-ray Absorption Fine Structure）等时间分辨的XAFS实验方法相比，该方法不需要更改光束线站的现有结构，能够与实现普通XAFS实验方法的光束线站兼容，特别适合上海光源XAFS光束线开展时间分辨XAFS实验方法的研究。论文在广泛调研了国内外相关光束线站QXAFS数据采集系统的基础上，开展了基于EPICS运行平台的运动控制和QXAFS数据采集系统的相关研究，主要包括以下工作： 1.针对上海光源XAFS光束线站现有的QXAFS数据采集系统的不足之处，完成了运动控制和QXAFS数据采集系统基于统一的运行平台的整体设计方案。在系统方案中，Scaler用于对高稳定运行的Bragg电机的控制脉冲的进行计数以获得单色光能量，高速ADC用于获取样品前后电离室的光电流信号，独立运行的硬件触发信号源则为两者分别提供1MHz的硬件触发信号用于实现控制与数据采集系统的硬件同步。在实验室分别完成了三个部分的硬件配置、软件开发和离线调试并对整体软硬件系统进行了集成和联调。 2.在上海光源XAFS光束线站开展了基于EPICS的QXAFS数据采集系统的研究和测试。研究测试了提高QXAFS实验方法信噪比的相关实验条件，包括选择ADC采样率、确定Bragg电机驱动器细分数，在能量扫描过程中进行T2电机补偿；测试了电流放大器的配置参数对QXAFS谱的影响以及不同积分时间对QXAFS谱在高k区的平滑性的影响。经过与标准的7.5um的标准铜箔样品的普通XAFS谱相对比，证明了基于EPICS的QXAFS数据采集系统不仅采集速度快、采集到的QXAFS谱的信噪比好，而且整个系统具有很高的稳定性和可重复性。应用该系统在上海光源XAFS光束线站开展了对Au8团簇加入盐酸后的刻蚀反应的原位过程的研究。在加入盐酸后的不同时间点取出溶液测试其QXAFS谱以了解Au8团簇加入盐酸后的刻蚀机理。实验结果表明Au8等团簇金核原子数目比较少，Au-Au峰不明显。而非金属配位峰只有在反应的初期有比较大的变化，，说明该反应速度过快，需要尝试降低反应速度来获得更为丰富的中间过程信息。该应用研究验证了基于EPICS的QXAFS数据采集系统已能满足开展动态原位过程研究的要求。
[Abstract]:With the emergence and development of synchrotron radiation, synchrotron radiation experiments of various new emerging. The development of synchrotron radiation new experimental methods and use them to carry out research on scientific problems in related fields has become an important content of.X ray synchrotron radiation field absorption fine structure (X-ray Absorption Fine Structure, XAFS) is an analysis method with the development of synchrotron radiation source and gradually mature strong structure.
Different from ordinary XAFS experimental methods used by the "step-by-step" mode of data acquisition, fast scanning X ray absorption fine structure (Quick-scanning X-rayAbsorption Fine Structure, QXAFS) by using the experimental method of "data collection on-the-fly", can be in double crystal monochromator (Double Crystal Monochromator, DCM) can complete the data acquisition work of a XAFS in order to obtain experimental spectra of the second sample process for the movement of QXAFS in the experimental.QXAFS spectra method, suitable for carrying out the catalytic industry, chemical process, research on dynamic process in situ biological sensing and material science. XAFS (Energy-Dispersive X-rayAbsorption Fine and energy dispersive Structure, EDXAFS), XAFS (pump-probe X-ray pump probe Absorption Fine Structure XAFS) and other experimental methods for time-resolved compared, this method does not need to change the beam line station The existing structure can be compatible with the beamline station that implements the common XAFS experiment method, and is especially suitable for the time resolved XAFS experiment method of XAFS beam line in Shanghai light source.
On the basis of extensive research on the related data acquisition system of beamline QXAFS at home and abroad, the related research on motion control and QXAFS data acquisition system based on EPICS operation platform is carried out.
1. for the shortcomings of Shanghai light source XAFS beamline QXAFS existing data acquisition system, complete the motion control and data acquisition system for QXAFS overall design scheme based on unified operation platform. In the system scheme, Scaler for Bragg motor for high stable operation of the control pulses were counted to obtain monochromatic light energy. High speed ADC for the current signal acquisition chamber samples before and after the independent operation of the hardware trigger signal source is respectively provided 1MHz hardware trigger signal to realize control and data acquisition system hardware synchronization. Three parts hardware configuration were completed in the laboratory of software development and off-line debugging and the whole hardware system the integration and debugging.
2. in Shanghai light source XAFS beam line station to carry out the research and test of QXAFS data acquisition system based on EPICS. The study tested QXAFS experimental methods improve signal-to-noise ratio of the experimental conditions, including the selection of the sampling rate of ADC, Bragg motor subdivision, T2 motor compensation in energy scanning process; test configuration parameters the current amplifier of QXAFS spectrum and the influence of different smooth integration time on QXAFS spectrum in the high K region. Through 7.5um and standard standard samples of ordinary XAFS spectrum copper foil for comparison, that based on the number of QXAFS EPICS data acquisition system not only acquisition speed, good signal-to-noise ratio collected by QXAFS spectrum, and the system has high stability and repeatability.
The application of the system to carry out the research on the process of standing in situ etching reaction of Au8 clusters after the addition of hydrochloric acid in Shanghai light source beamline XAFS. Remove the solution to test its QXAFS spectrum to understand the mechanism of etching Au8 clusters after adding hydrochloric acid. At different time points after addition of hydrochloric acid the experimental results show that the Au8 clusters of gold atom the number is relatively small, the Au-Au peak is not obvious. Instead of metal coordination peaks only have relatively large changes in the initial reaction, the reaction speed is too fast, need to try to reduce the reaction speed to obtain more information rich. The intermediate process of application of validation of the QXAFS EPICS data acquisition system can meet research in situ dynamic process based on the requirements.

【学位授予单位】：中国科学院研究生院（上海应用物理研究所）
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TL544;TP274.2

【参考文献】