Improvement of Interference Fringes Analysis to Obtain Accurate Soret Coefficients

In this study, we proposed a moved-view analysis, a method for obtaining the Soret coefficient S T by analyzing the interference fringe change during field-of-view movement in the steady state. This analysis was designed to solve the problem that the sign of the concentration gradient could also be reversed if the plot of the concentration distribution was only slightly shifted owing to the narrow field of view. The data obtained from the experiment conducted to measure S T at the International Space Station were analyzed using moved-view analysis. For the moved-view analysis, the linearity of the concentration distribution induced by the Soret effect is larger than that for the method without field-of-view movement, and a more reliable S T can be obtained. The analysis error that sometimes occurred when the laser wavelength switched led to the underestimation of the phase change Δ ϕ , resulting in generating the data with low linearity. This unreliable data should be removed.