High Pressure Synchrotron Sources

Synchrotron Methods in High Pressure Research

The PIs working in this area: Wenge Yang

Significant advances in high pressure research have been made in recent years together with rapid progress in synchrotron radiation techniques. Brilliant synchrotron x-rays provide excellent probes for micron-scale samples for a variety of experimental measurements at high pressure. Complex samples at increasingly higher pressures and more extreme temperatures are being studied with higher accuracy probes for characterization of structural, electronic, and phonon properties. Many previous technical limitations in capability, precision and accuracy are being removed through optimization of radiation sources, optics, sample environment, experimental configuration, software control, and detectors and analyzers.

The sample crystals for high-pressure studies are relatively small and absorption in the diamond-anvil cell reduces the diffracted intensity still further. The high x-ray flux of synchrotron radiation can improve the counting statistics dramatically –particularly for small-molecule systems containing light elements. The x-ray wavelength of the synchrotron beam can be tuned to shorter wavelengths than those offered by laboratory sealed-tube sources. A shorter wavelength not only improves resolution (sinθ/λ) but it also increases the number of accessible "layers "of reflections in the quasi two-dimensional data set. The diamond-anvil cell introduces a relatively high and textured background which makes the integration of diffracted intensities more difficult –particularly for weak reflections. The low-divergence of the beam can worsen the texture in the background, thereby, improves the signal to noise ratio.

High pressure synchrotron techniques include:
         X-ray diffraction (angle dispersive and Energy dispersive)
         X-ray total scattering/Pair distribution function
         X-ray absorption
         Nuclear Resonance scattering
         Inelastic x-ray scattering
         X-ray image
         Raman scattering
         Infrared spectroscopy
         Neutron scattering

In HPSTAR, scientists use these techniques to probe minute samples at high pressure and develop the new analytical tools.