Nuclear Techniques ›› 2015, Vol. 38 ›› Issue (5): 50101-050101.doi: 10.11889/j.0253-3219.2015.hjs.38.050101

• SYNCHROTRON RADIATION TECHNOLOGY AND APPLICATIONS •     Next Articles

QXAFS data acquisition and control based on DCM

ZHOU Yongnian1,2 ZHANG Zhaohong1,2 LIU Ping1 GU Songqi1 JIANG Zheng1 LI Yongping1 ZHENG Lifang1   

  1. 1(Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Zhangjiang Campus, Shanghai 201204, China) 2(University of Chinese Academy of Sciences, Beijing 100049, China)
  • Received:2015-03-17 Revised:2015-03-27 Online:2015-05-10 Published:2015-05-08

Abstract:

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 (DAQ) of QXAFS is developed in LabVIEW. Purpose: The present QXAFS control system at the XAFS beamline is using LabVIEW based DAQ 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 (GUIG). 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 achieved at the XAFS beamline at SSRF. It has great practical significance for carrying out fast time-resolved QXAFS experiment at SSRF.

Key words: QXAFS, EPICS, DCM, SSRF