Large monocrystal mfg. plant - where very large mono:crystals of potassium chloride, doped caesium iodide or similar materials can be drawn out of melt in sealed chamber

摘要

The plant includes a stationary upper chamber (a) contg. a vertical shaft, which can be rotated and driven vertically. On the bottom end of the shaft is a holder for a seed crystal. A lower chamber (b) can be driven horizontally on a chassis until it is below chamber (a) and can then be raised to make a sealed chamber (a,b). In chamber (b) is a heated crucible contg. a melt, from which the seed crystal can draw a large monocrystal vertically upwards into chamber (a). Chamber (b) is then replaced by a thermally-insulated holding chamber (c) into which the large monocrystal can be lowered. When the large monocrystal is in chamber (c), the shaft can be unscrewed from the seed holder, and chamber (c) can be moved e.g. into a holding furnace for controlling cooling. Mfr. of monocrystals above 200 mm. in dia. and length over 300 mm., with wt. above 10 kg. for optical devices or scintillators. The crystals are made e.g. of NaCl, KCl, KBr, NaBr, LiF, CaI doped with Ti or Na; or semiconducting Ge- or Si- monocrystals.