A novel viscosity measurement technique was developed in which angular deflection-oscillation of a sealed quartz ampoule containing a semiconductor melt is measured upon application of a rotating magnetic field. This paper provides a theoretical basis for this novel method. Equations for coupled fluid flow and ampoule torsional oscillation were solved numerically. The predictions of the melt flow and ampoule oscillation were in good agreement with the experimental data. The results also showed that both electrical conductivity and viscosity could be calculated from the experimental data by a numerical fitting procedure. The transient velocity of the melt caused by the rotating magnetic field was found to reach steady state in about one minute, within which both the electrical conductivity and the viscosity of the melt can be obtained. This is a significant improvement over the existing oscillation cup method, which requires about one hour of measurement to obtain viscosity.

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