New XAFS Facility for In-Situ Measurements at Beamline C at HASYLAB

Abstract

A XAFS‐experiment allowing for in‐situ experiments has been set up at DORIS bending magnet beamline C. For that purpose, a new double‐crystal, UHV‐compatible monochromator with fast scanning capability was designed. This fixed‐exit monochromator uses two crystal sets on a common central rotation axis driven by an ex‐vacuo goniometer. Bragg angles range from 5° to 55.5° resulting in a total energy range 2.3 – 43.4 keV using Si(111)/(311) crystal sets. Crystal pairs can be remotely selected by translating the vacuum chamber. Energy encoding is performed using an optical encoder system. The standard XAFS sample environment is set‐up in vacuo and can be adapted for special sample environments. For in‐situ experiments, the beamline is equipped with twelve gas lines. An exhaust line allows toxic/reactive gases to be handled. As an initial performance test of the instrument, Ti, Cr, Fe and Cu XAFS and Ce K‐shell QEXAFS measurements were performed.