Data-collection System For High-throughput X-ray Absorption Fine Structure Measurements

The Shanghai Synchrotron Radiation Facility(SSRF) is an intermediate energy, third generation light. In the first phase, seven beamlines were constructed within the SSRF project budget. Since the initial beamlines have only seven experimental stations including one for X-ray absorption fine structure(XAFS), the demands on beamtime has been in great urgency, and currently only about 1/4 of applications can be approved and allocated to do experiments. To solve this problem, more XAFS beamlines are required or the present beamtime should be used more efficiently.The high-throughput(HT) technique, which allows multiple(from several up to hundreds) materials to be tested sequentially without stopping the experiment, is powerful to resolve this problem. During the past two decades, HT method has been received much attention in various research fields such as the optimization on the conversion and selectivity of new catalyst, measurements of reaction kinetics and spectroscopic methods including infrared spectroscopy, Raman spectroscopy, X-ray fluorescence, fluorescence microscopy, imaging polarimetry, nuclear magnetic resonance spectroscopy, X-ray diffraction and XAFS. Particularly, the HT technique has been well established in many XAFS beamline of advanced synchrotron radiation facilities internationally. However, this technique has not been established at BL14W1 beamline of SSRF.Based on widely investigation and survey of the high-throughput XAFS data-collection system at related home and abroad beamlines, we carry out the research on the high-throughput XAFS data collection system at BL14W1 at SSRF. The work mainly includes:1. The set-up of high-throughput XAFS data-collection system, which is based on Experimental Physics and Industrial Control System(EPICS) is established at XAFS beamline of SSRF. Besides the general XAFS instruments(experimental stage, detectors, laser pointer, etc.), the HT XAFS measurement also requires a high-precision 2-D stage(x,z) and equipment of motor control system.2. The software of high-throughput XAFS data-collection system based on EPICS is established at BL14W1 beamline of SSRF. The core of the EPICS is IOC(Input/output Controller). 2-D stage and counter are controlled by different IOCs. High-precision 2-D stage(x, z) control system contains an IOC and the IOC loads one database telling it what to do. The IOC of counter is expressed by EPICS database records, StreamDevice protocol files and the IOC startup command file(st.cmd). StreamDevice is a generic EPICS device support for devices with a "byte stream" based communication interface. Examples for this type of communication interface are serial line(RS-232, RS-485,), GPIB and TCP/IP. This job has been done by BL14W1 beamline staffs and we can access the data of counter by inputting the PV(Process Variable) name attached to the device. CSS(Control System Studio) was selected to develop Graphical User Interface(GUI), which allows the experimenter to operate the HT measurement. Additionally,JavaScript are selected as the scripting environment. JavaScript is applied to describe:(1) how to select scan model;(2) when to collect XAFS data;(3) when to switch samples;(4) how many samples to be scanned.3. We have demonstrated the successful HT XAFS system by running experiments on two groups of copper-ceria catalysts, each of which contains 8 different powder samples. The data-quality is very high and the profile is fairly smooth without any observable glitches. Further analysis on the while-line of X-ray absorption near edge spectra(XANES) determined the different oxidation states of Ce atom in every copper-ceria sample. So, the HT XAFS results were identical to those tested by conventional XAFS mode. However, the total collection-time was only 160 min, significantly less than the conventional XAFS mode(250 min). Furthermore, this data collection system of HT XAFS measurements can be directly applied in fluorescence mode with the corresponding sample holder and the system is the necessary prerequisite for HT in-situ XAFS/QXAFS measurements at BL14W1 station of SSRF.