Thermophysical Properties of Molten Silicon

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A new experimental apparatus based on the laser induced capillary wave technique by using pulsed CO_2 laser (wavelength: 10.6 μm, pulse width: 50 ns, output energy: 65 mJ) as a heating source has been developed. In this method, pulsed two high-power laser beams intersect on a sample surface and they generate spatially sinusoidal temperature distribution. The temperature distribution of the thermal grating creates capillary wave on the surface by the thermal expansion (the amplitude of the wave is about 10 nm). The capillary wave is detected by a diffracted probe beam at the heated area on the surface.The results obtained from the present research are summarized as follows.1. We have developed a new experimental apparatus by using pulsed CO_2 laser and established experimental techniques to detect a stable signal with this apparatus.2. The signal from low viscosity materials such as toluene showed the damping oscillation. In the case of high viscosity materials such as glycerol, we detected the overdamped wave. The application of laser induced capillary wave method has considerable potential for the measurement of wide viscosity range.3. Detected signal from toluene was very well in agreement with theoretically calculated wave forms considering the temperature dependence of surface tension.