In situ ultrasonic interface tracking for photovoltaic silicon directional solidification
Résumé
This paper presents an experimental validation of an in situ ultrasound technique for the tracking of the interface of photovoltaic silicon during directional solidification. Ultrasound pulses are introduced from the top inside the melt at 1500◦C via the tip of a carbon glass wave guide directly plunged into the liquid. The experiment involves a small load of silicon in a prototype furnace in which several runs of solidification have been conducted. The main novelty of the developed wave guide relies on its reusability and its very good acoustical and chemical compatibility, overcoming the pollution of the liquid phase. We expose time of flights analysis, assuming normal incidence, to extract not only the location of the liquid-solid interface but also the longitudinal celerity of sound waves in the growing silicon crystal.
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