Shear cell development for diffusion experiments in FOTON satellite missions and on the ground with consideration of shear induced convection

Abstract

A shear cell technique was developed to obtain exact diffusion data. The shear cell in this study was designed for the utilization under g conditions, especially in the FOTON M2 mission, but also under 1g conditions. To minimize the influence of the shear convection, the cell size, the rotation system and the speed of the discs were optimized. To minimize free surfaces, which can cause Marangoni convection, a reservoir system providing pressure on the liquid was introduced. Using this FOTON shear cell we performed short time diffusion experiments in the In Sn system in a parabolic flight and under 1g conditions to investigate the influence of the shear convection quantitatively. As a result, the influence of the shear convection was so small that the mean square diffusion depth caused by the shear convection was in the order of 10 7m2, which is smaller than 1 of the typical value in a standard diffusion experiment using the FOTON shear cell. By using this result a correction method for the evaluation of the diffusion coefficient was established. In several ground experiments, the FOTON shear cell showed the same diffusion coefficients as from g reference experiments within the range of errors and no obvious indication of Marangoni convection was detected. From these results we confirmed that the FOTON shear cell can be applied to g experiments and ground based experiments as wel