基于DCM的QXAFS数据采集与控制  

QXAFS data acquisition and control based on DCM

作　　者：周永年[1,2] 张招红[1,2] 刘平[1] 顾颂琦[1] 姜政[1] 李勇平[1] 郑丽芳[1] 

机构地区：[1]中国科学院上海应用物理研究所,张江园区上海201204 [2]中国科学院大学,北京100049

出　　处：《核技术》2015年第5期1-7,共7页Nuclear Techniques

基　　金：国家自然科学基金(No.11275258;No.11135008)资助

摘　　要：快速扫描X射线精细结构谱(Quick-scanning X-ray Absorption Fine Structure,QXAFS)是测定特定吸收原子近邻环境结构的一个强有力的工具,已广泛应用在固体物理、催化剂和蛋白质分子等领域。双晶单色器(Double Crystal Monochromator,DCM)是上海光源XAFS光束线站的关键设备,它能够将一定波长范围内的白光单色化,并将单色光束稳定出射至下游光学元件。上海光源XAFS光束线站数据采集程序是在Lab VIEW环境下开发的,而其采用了步进电机的DCM控制系统则采用了基于分布式控制的实验物理及工业控制系统(Experimental Physics and Industrial Control System,EPICS)。由于运行环境不同,两者在装置联动时不可避免存在网络延时的缺陷并使得XAFS谱发生变形和不连续的问题。在EPICS环境下产生硬件触发信号并用其同步采集电离室和步进电机的信号,实现QXAFS数据的实时采集与控制。对标准铜箔样品进行了实验测试,结果表明该方法不仅可以保证系统获得较高的信噪比,而且可以在小于8 s的时间内获取一个完整的QXAFS谱,在小于500 ms时间内获得一个近边结构谱。该系统的实现对上海光源开展快速时间分辨的QXAFS实验具有重要的应用意义。Background： Quick-scanning X-ray Absorption Fine Structure （QXAFS） is a powerful tool for measuring and determining the environmental structure of specific absorption atoms. It has been widely applied in the fields of solid state physics, catalyst and protein molecules. Double Crystal Monochromator （DCM） is a key device at XAFS beamline of Shanghai Synchrotron Radiation Facility （SSRF）. It is used to change the certain wavelength of white light to monochromatic light and pass it to follow-up optical elements. The Bragg motor of the DCM is a step motor and its control system adopts Experimental Physics and Industrial Control System （EPICS） while the data acquisition system （DAS） of QXAFS is developed in LabVIEW. Purpose： The present QXAFS control system at the XAFS beamline is using LabVIEW based DAS which contains some drawbacks, such as the energy drift and spectrum distortion. It is running in the Windows operating system environment while the DCM control system is running in Linux. The network transmission delay occurs at the communication between the two different kinds of system. The aim of this study is to design and implement fast time-resolved QXAFS data acquisition system based on EPICS that can solve these defects. Methods： Two 1-MHz hardware trigger signal is generated and used to collect the signals of ionization chambers and the step motor synchronously in the new design. The software of the system is developed in EPICS and runs in the Linux operating system environment. The experimental method is implemented by python routine which is also integrated into the Graphical User Interface （GUI）. Results： Conventional XAFS spectrum and four QXAFS spectra with an energy range of 1.2 keV at the Cu K-edge have been collected in less than 8 s at the XAFS beamline. The experimental results indicate the QXAFS system can ensure a good signal-to-noise ratio （SNR）, as well as a perfect stability and repeatability. Conclusion： The QXAFS data acquisition system based on EPICS is

关 键 词：快速扫描X射线精细结构谱 实验物理及工业控制系统 双晶单色器 上海光源 

分 类 号：TL99[核科学技术—核技术及应用]