Physics
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufmmr21c0031k&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #MR21C-0031
Physics
3919 Equations Of State, 3924 High-Pressure Behavior, 3954 X-Ray, Neutron, And Electron Spectroscopy And Diffraction
Scientific paper
Laser-heated diamond anvil cell (DAC) experiments are currently the only static experimental devices that allow to study planetary materials at the high pressure and temperature conditions that are characteristic of deep planetary interiors. Due to the small sample dimensions inhomogeneities of the thermal structure in the sample may be expected. Experimental observations that are commonly made along the diamond anvil cell axis average the temperature field in the x-ray volume. However, in order to sample a well defined thermodynamic state it is important to minimize these variations. Thus a comparative study of the thermal structure in different experimental assemblies may aid in choosing geometry/heating combinations that minimize thermal variations in the sample and thus most closely approach a homogeneous thermodynamic state. Finite element (FE) calculations were performed in a cylindrical geometry following methods similar to Kiefer and Duffy (2005). In this study, we have performed the first FE simulations of metallic samples in the laser- heated DAC. In addition, we have considered single-sided and double-sided heating techniques representative of using a near-IR laser operated in either TEM00 or TEM01 laser modes as well as the microfurnace technique. We find that the TEM01 heating mode results generally in a more homogeneous temperature field as compared to TEM00. For double-sided TEM00 heating we find that radial temperature variations depend more strongly on sample thickness and that they increase for thinner samples. This effect is strongly reduced if double-sided TEM01 heating is used. Single-sided laser heating techniques shows the largest axial temperature variations in the sample of up to ~25% of the maximum temperature. For comparison these variations are less than ~5% in the double-sided laser-heating and microfurnace geometries. Thus our finite-element calculations suggest that currently the double-sided laser-heating (TEM01) and the microfurnace techniques are most suitable to approximate a well-defined thermodynamic state in metals in particular at high compression for thin samples.
Duffy Thomas S.
Kiefer Bernd
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