The laser-heated diamond-anvil cell (LH-DAC) is the only experimental tool able to create extreme static pressures (P > 100 GPa) and temperatures (T > 3000 K) and it has had a major impact in high-pressure research and geophysics.
The conventional way to determine the temperature of a laser-heated specimen is by measuring the radiation emitted from the heated specimen using a diffraction spectrometer. However, those measurements only provide the temperature of the heated spot averaged over its area. This a technique works perfectly only for a uniform temperature distribution. However, the temperature under a laser has significant non-uniformity. Recently, flat top laser heating was used to study the elastic properties of platinum alloy by measuring the velocity of the skimming acoustical wave in iron at at 2580 K and 22 GPa in a DAC. For such measurements it is important to use an area with a flat temperature distribution. Further progress in the development of the laser heating techniques requires knowledge of the 2-D temperature field in a material induced by laser beam radiation.
Conventional techniques for the measurement of 2-D temperature distribution based on calibration of the digital signal from the camera in the infrared or visible ranges are not applicable for DAC due to priori unknown and non-uniform emissivity distribution in the sample. Several techniques were proposed to measure temperature distribution in a specimen heated by a laser . Recently, a multispectral imaging radiometry (MIR) system for measuring temperature gradients of specimens under high pressure heated by laser in a DAC (LH-DAC) was developed by Campbell.We demonstrate that combining the laser heating system in a diamond anvil cell (LH-DAC) with a tandem acousto-optical tunable filter (LH-DAC-TAOTF) allows measurement of the temperature distribution under laser heating of a specimen under high pressure in a DAC. The main component of the system is an imaging TAOTF synchronized with a video camera. The use of the TAOTF also makes it possible to visualize the infrared (1064 nm) laser beam, which is invisible to the human eye. The distribution of the temperature T(x,y) was then determined on surface of two Pt plates loaded in DAT at high pressures by fitting the actual signal to Planck's equation at each point of the specimen's surface
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| Topics | : | Posters: Experimental and Analytical Techniques |
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