A system and procedure for simultaneously monitoring temperatures along the melt and crystal axis, those on the external surface of the quartz ampoule and in various elements of the "Polyzone" facility's thermal unit have been developed. A detailed 2D-picture has been obtained of spatial-time temperature fields evolutions in the ampoule and in the thermal unit during the crystal growth process using directed crystallization. A mathematical model has been created and parametrical calculations of the growth process have been carried out. (C) 2002 Elsevier Science B.V. All rights reserved.