The greater demand for high-quality large-diameter crystals has led to the robust idea of a free-flying solar-powered furnace satellite, whereby the buoyancy-driven convection effects are almost nonexistent, and diffusion-controlled crystal growth with minimal radial segregation is promoted. In the proposed solar furnace, a paraboloid of revolution imaging concentrator is used to focus the sun's radiation onto an ampoule which holds the solid charge to be processed. The charge will start melting in the vicinity of the coal point, after which it is translated in order for the melt to resolidify as a single crystal. A ray-trace method has been developed to determine the incident concentrated solar heat flux on the ampoule surface for a perfectly-aligned configuration with an incoming uncoluminated beam. A transient 2-dimensional conduction problem with phase change is formulated, which is solved using the commercial code FIDAP. By ignoring the participation of the ampoule in the heat transfer process, preliminary results highlighting the feasibility of growing GaAs, Ge and Si crystals with diameters of the order of 20 cm using the solar furnace satellite concept are presented. The transient temperature fields within various charge materials during the heat-up process are quantified. The resulting melting pattern is observed to be more uniform along the charge when compared to the idealized limiting case of columnated beams.
Temperature fields within large-diameter crystals grown on a solar furnace satellite
Temperaturfelder in großen in einem Satelliten mit Sonnenofen gewachsenen Kristallen
1994
7 Seiten, 6 Bilder, 2 Tabellen, 7 Quellen
Aufsatz (Konferenz)
Englisch
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