Researchers using the HP-CAT Sector 16 beamlines at the APS have developed novel controlled-geometry samples for a laser-heated diamond-anvil cell. This work was completed using nanofabrication techniques, in which a transparent sample layer (SiO2) is sandwiched between two laser-absorbing layers (Ni).
The laser-heated diamond-anvil cell coupled with synchrotron-based X-ray diffraction (XRD) is a powerful tool to measure unit-cell volume to determine bulk modulus and thermal expansion, which are required for accurate interpretations of seismic wave speeds and reliable modeling of the structure, dynamics, and composition of Earth’s deep interior
We have fabricated novel controlled-geometry samples for the laser-heated diamond-anvil cell (LHDAC) in which a transparent oxide layer (SiO2) is sandwiched between two laser-absorbing layers (Ni) in a single, cohesive sample. The samples were mass manufactured (>104 samples) using a combination of physical vapor deposition, photolithography, and wet and plasma etching. The double hot-plate arrangement of the samples, coupled with the chemical and spatial homogeneity of the laser-absorbing layers, addresses problems of spatial temperature heterogeneities encountered in previous studies where simple mechanical mixtures of transparent and opaque materials were used. Here we report thermal equations of state (EOS) for nickel to 100 GPa and 3000 K and stishovite to 50 GPa and 2400 K obtained using the LHDAC and in situ synchrotron X-ray microdiffraction. We discuss the inner core composition and the stagnation of subducted slabs in the mantle based on our refined thermal EOS.
Jeffrey S. Pigott, Derek A. Ditmer, Rebecca A. Fischer, Daniel M. Reaman, Rostislav Hrubiak, Yue Meng, Robert J. Davis and Wendy R. Panero, “High-pressure, High-temperature Equations of State Using Nanofabricated Controlled-geometry Ni/SiO2/Ni Double Hot-plate Samples,” Geophysical Research Letters, Volume 42, Issue 23, pp. 10,239–10,247, 16 December 2015, DOI: 10.1002/2015GL066577.