Diffusion measurements using the shear cell technique: Investigation of the role of Marangoni convection by pre-flight experiments on the ground and during the Foton M2 mission

An experimental investigation on the disturbing influence of the solutal Marangoni convection during diffusion measurements is presented. We used the systems Sn-Bi, Pb-Ag and Sn-In with decreasing differences in surface tension. For all systems we measured surface tension and - under varying free surface conditions - diffusion coefficients. We succeeded in measuring diffusion coefficients on the ground under nearly non-free surface conditions. The results are compared with the results of the FOTON M2-satellite mission with similar μg-experiments. We show that temperatures from around 400 °C to about 800 °C and the degree of free surfaces influences strongly the measured value for the diffusion coefficient.