Analysis Method Using Two-Wavelength Mach-Zehnder Interferometer for the Measurement of Soret Coefficients in Soret-Facet Mission on ISS

Momoko Tomaru*, Takuma Osada, Isamu Orikasa, Shinsuke Suzuki, Yuko Inatomi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


The Soret-Facet mission was conducted under microgravity conditions to measure the Soret coefficient (S T ) for salol/tert-butyl alcohol using a two-wavelength Mach-Zehnder Interferometer (2-MZI). The 2-MZI is useful in the simultaneous measurement of temperature and concentration in binary mixtures. However, the simultaneous analysis of the 2-MZI had the limitation in accurate determination of S T because of the uncertainties in the experimental values of coefficients of refractive indices. To reduce the uncertainties in the measurement of coefficients of refractive indices, this paper describes an alternative method to measure temperature and concentration individually, using the 2-MZI. This alternative method was applied to analyze the microgravity data of Soret-Facet mission and the changes of temperature and concentration were shown at each wavelength. The coefficients of refractive indices and S T were corrected based on matching the two changes of temperature or concentration so that two or three of the following constraints were satisfied: fulfill the deviation ranges of coefficients; minimize the difference between two gradients; and match with thermocouples. This correction led to the reduction in dispersions of analyzed values in the simultaneous analysis, and clarified that it is necessary to improve not only the coefficients of refractive indices but also the ratio between phase changes in the simultaneous analysis. The results indicated that the separate analysis for the 2-MZI can estimate the coefficients of refractive indices and is useful for measuring the Soret coefficient in binary mixtures.

Original languageEnglish
Pages (from-to)49-59
Number of pages11
JournalMicrogravity Science and Technology
Issue number1
Publication statusPublished - 2019 Feb 1


  • Microgravity experiment
  • Salol/tert-butyl alcohol
  • Soret effect
  • Two-wavelength Mach-Zehnder interferometer

ASJC Scopus subject areas

  • Modelling and Simulation
  • General Engineering
  • General Physics and Astronomy
  • Applied Mathematics


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