DESIGN AND FEASIBILITY OF QUICK EXAFS SCANS FOR A BROOMSTICK DOUBLE-CRYSTAL MONOCHROMATOR AT PLS BEAMLINE

A data-collection technique for quick extended X-ray absorption fine-s tructure spectroscopy (QEXAFS) was developed with a new 'broomstick' d ouble-crystal monochromator, which has been installed for X-ray absorp tion fine-structure (XAFS) applications at the Pohang Light Source. Th e monochromator operates in a fixed-exit scan mode as the Bragg angle is varied from 8 to 80 degrees, corresponding to 2-14 keV, using an Si (111) crystal. The monochromator scan capability was investigated by a nalysing EXAFS data quality from step-scan and from continuous rotatio n of the Bragg crystal reflection angle. In our fast continuous-scan d esign, the electronic pulsing speed of the step motor is adjustable to avoid the monochromatic beam instability caused by serious mechanical resonance. The feasibility of QEXAFS scanning is demonstrated by a ty pical EXAFS scan (e.g. 1 keV range) being taken within 1 min.