Avtomated pulling of large-diameter alkali-halide scintillation single crystals from melt and control of the activator distribution therein


Institute for Single Crystals, National Academy of Sciences of Ukraine, 60 Lenin Ave., 310001 Kharkiv, Ukraine

Received May 14, 1998

Principles of the high-productivity automated pulling method of large-diameter alkali-halide single crystals have been described. At the radial growth stage, the melt geometry is varied continuously due to its level elevation in a conical crucible provided by the melted raw material feeding controlled by the signal of a lifting electrocontacting probe. The melt level remains constant at the stage of the longitudinal growth. Time intervals between successive feeding operations are used in the automated diameter control system as the informative parameter. The automatic system based on this principle provides the crystal diameter control to an accuracy better than 1% at the diameter of 400-450 mm and the pulling rate of 6-6.5mm/h.
The method has been mastered in the industrial production of alkali-halide scintillation single crystals.

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