Thermophysical Properties of Molten Silicon

研制了一种基于激光诱导毛细波技术的新型实验装置，该装置以脉冲CO_2激光器（波长10.6 μm，脉宽50 ns，输出能量65 mJ）为加热源。在该方法中，两束高功率脉冲激光束在样品表面相交，产生空间正弦温度分布。热光栅的温度分布在热膨胀的作用下在表面产生毛细波（振幅约为10 nm）。在表面加热区用衍射探测光探测毛细波，得到了以下结果.我们研制了一种新型的脉冲CO_2激光器实验装置，并建立了利用该装置探测稳定信号的实验技术.来自低粘度材料如甲苯的信号显示出阻尼振荡。在甘油等高粘度材料的情况下，我们检测到过阻尼波。激光诱导毛细波法在宽粘度范围的测量中具有很大的应用潜力.从甲苯中检测到的信号与考虑表面张力的温度依赖性的理论计算的波形非常一致。

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.