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1 December 1991 Laser beam deflection: a method to investigate convection in vapor growth experiments
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While the growth of bulk crystals and thin layers from vapor is a method with increasing importance and great potential, the theoretical understanding of this technique is quite limited. In particular, the influence of impurities and natural convection on the transport mechanism is not well understood. Density gradients in the vapor phase can be measured by the deflection of a laser beam traversing the growth cell perpendicular to the main direction of material transport. The suitability of this method has been demonstrated in a laboratory setup using iodine as reference material. Optical gradients dn/dz < 10 exp -6/cm can be detected when the region of transport has a depth of 1 cm. The results of the first experiments are in the range predicted by theory. However, to obtain more reliable and precise data, the thermomechanical properties of the total setup have to be improved. Since the beam deflection technique can be realized in a small volume and does not need exhaustive diagnostics instrumentation or data processing, it can easily be adapted to a spaceflight experiment.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Harald Lenski and Michael Braun "Laser beam deflection: a method to investigate convection in vapor growth experiments", Proc. SPIE 1557, Crystal Growth in Space and Related Optical Diagnostics, (1 December 1991);

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