First phase commissioning of high pressure XAFS setup at ED-XAFS beamline, Indus-2 synchrotron radiation source, India

Abstract

In this work, we report the first-phase commissioning of High Pressure setup at XAFS beamline (Bl-08) of Indus-2. This involved installation of vertically focusing bendable elliptical mirror to obtain~50 μm spot size, as required for Diamond Anvil Cell-based High Pressure XAFS experiment. We present details of the mirror alignment procedure, observed deviations from design goals and suggestions for improvement. We provide realistic estimate of the kind of experiments that can be performed in the current setup.

First high-pressure XAFS results at the bending-magnet-based energy-dispersive XAFS beamline BL-8 at the Indus-2 synchrotron facility

“…The target is to strengthen signal statistics by improving (i) horizontal focusing with further bending of the polychromator and (ii) vertical focusing with a bendable elliptic mirror purchased from SESO (http://seso.com/newservices/x-rays/x-ray-mirrors/). The mirror was preliminarily installed in the first phase of commissioning (Ramanan et al, 2015) and has been motorized recently for precise alignment in the future. With these ammendments, we hope to extend the scope of HPXAFS at BL-8.…”

“…1: diamond anvils serve as X-ray windows for incident (I 0 ) and transmitted (I t ) beam; XAFS is measured by = lnðI 0 =I t Þ. Sample size is small (D 250 mm) in order to raise pressure (P / 1/D 2 ) (Ramanan et al, 2015). This configuration poses two challenges for XAFS.…”

“…The second problem with the DAC is a weakening of the signal-to-noise ratio (i.e. poor statistics) due to X-ray absorption within the diamond windows (Ramanan et al, 2015). This could result in incorrect normalization for I 0 /I t ; further, the Fourier transform of the statistical noise could generate spurious peaks in r-space that interfere with the real structure.…”