Temperature gradients in high pressure multi-anvil cell

Temperature gradient through cylindrical Re furnace set in an octahedral assembly for Kawai-type of the multi-anvil high pressure apparatus was examined at a central temperature of 2500°C and pressures of 10.4-12.4 GPa, based on coesite-stishovite phase boundary in SiO2. The axial temperature showed a parabolic curve, which is approximated by a quadratic function between the temperature differences from the temperature at the hotspot and the distance from the sample center, equivalent to the hotspot, ΔT = −258.7L2 −16.8L (r2 = 0.99), where ΔT (°C) is the temperature difference between the center and at a point, and L (mm) is the distance of the point from the center. The estimated temperature gradient is around 260°C/mm at 2500°C. Here, the factors that influence the temperature gradient, such as the sample temperature, the shape and the material of the furnace, and the design of the cell assembly, are also discussed.