Characterising the sample environment in multianvil high-pressure experiments

The multianvil apparatus is used to generate conditions up to about 3100 K and 26 GPa with sample volumes of 1-12 mm(3). Because high pressures and temperatures are stable over long experimental run durations, this apparatus can be used to investigate phase equilibria, transformation kinetics, diffusion, electrical impedance and elastic properties at high temperatures and pressures. The control and characterisation of temperature, pressure, differential stress and oxygen fugacity, which are generally crucial in such studies, are discussed here with particular emphasis on the uncertainties involved.