The reason for this is not clear. It might be due to partial melting. Final deaccelelation is due to approaching the bottom. We observed shrink of Pt capsule during temperature quench. Due to small size of sphere and fast velocity, reading of sphere position is less accurate for this run.
Green circle shows present in-situ result.
Red square shows previous quench experiments. Kushiro and Brealey used piston cylinder device, whereas Kanzaki applied multi-anvil press. Number is pressure in GPa. From above figure, viscosity coefficients obtained in present in-situ experiments are about one order lower than those of previous quench experiments. Currently the reason for this is not clear at moment.