The quality of measurements at extreme conditions is governed by the size of the analytical probe relative to the size of the samples. High energy synchrotron x-ray probes have been used in high-pressure studies for decades. However, at the existing dedicated high pressure facilities, the dimensions of probes have been limited to 2-5 microns, which has become a key limitation to resolve properties of materials at megabar pressures where significant differences occur on the sub-micron scale.
A team led by Lin Wang and including scientists at Carnegie, the Advanced Photon Source, Stanford University, and National Cheng Kung University (Taiwan) has broken the micron barrier in these megabar pressure measurement by introducing nanoscale beams, an order of magnitude smaller than the existing high pressure x-ray probes, into high pressure studies. Their study, published in Proceedings of the National Academy of Sciences, show that the use of nanoscale x-ray probes overcomes several key limitations in the study of materials up to multimegabar pressures. Nanoscale probes readily resolve signals from individual materials, between sample and gasket, peak pressure and pressure gradient at submicron length scale. These beams also enable single-crystal x-ray diffraction studies in nominally polycrystalline samples at ultrahigh pressure. These capabilities have potential for driving toward higher maximum pressures and further miniaturization of high-pressure devices [Wang et al., Proc. Nat. Acad. Sci.(2010)].