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A physical model for electromagnetic control of local temperature gradients in a Czochralski system.
, M. Röder
, J. Pal
, G. Gerbeth
Forschungszentrum Dresden--Rossendorf, Institute of Safety Research, P.O. Box 510119, 01314 Dresden, Germany
Magnetohydrodynamics 46, No. 4, 353-362, 2010 [PDF, 1.42 Mb]
The shape of the solidification front and the related mono-crystalline growth in the Czochralski crystal growth process is thought of being strongly influenced by the ratio of the horizontal and the vertical temperature gradient r∗ = ∆Th / ∆Tv at the triple point liquid-solid-atmosphere, which ratio desirably should be in the order of unity. A liquid metal model experiment was therefore built that allowed studying r∗ under the influence of magnetic fields. The cylindrical liquid metal column was homogeneously heated from below, whereas on top the heat was extracted in a centrical region covering only one third of the surface in order to simulate the growing crystal. Without flow control, r∗ ≈ 3 is far removed from unity. It was then possible to reach the target value r∗=1 for any temperature difference between the bottom and the top at a moderate field strength while applying a rotating magnetic field. Figs 9, Refs 6.