DEVICE FOR MONITORING THE PROGRESS OF CRYSTALLIZATION OF A BATH OF MOLTEN MATERIAL IN A DIRECTIONAL SOLIDIFICATION PROCESS EMPLOYING ULTRASOUND

摘要

The invention relates to a device for monitoring the progress of crystallization of a bath of molten material carried out within an insulating chamber of a crystallization furnace according to a directional solidification process. Said device comprises an ultrasound source including n sets (n being an integer =1), each set including a transducer capable of emitting an ultrasonic wave, connected to a waveguide capable of guiding the ultrasonic wave, produced by means of said transducer, toward the vapor-liquid interface of the liquid bath; an ultrasound detector including at least 2n sets, each set including a waveguide connected to a transducer capable of detecting an ultrasonic wave, said waveguide being capable of guiding an ultrasonic wave toward said transducer. Each source and each detector are placed above the vapor-liquid interface of the liquid bath in separate positions such that the ultrasonic wave produced by means of a source transducer impinges on the vapor-liquid interface at an acute angle relative to the normal to said interface and that said ultrasonic wave, reflected by the vapor-liquid interface at the same acute angle, is detected by a detector transducer. The transducers are located outside the chamber and the waveguides pass through the wall of said chamber. The waveguides include a wave entry surface and a wave exit surface, a lateral surface connecting said two surfaces, the surface of the waveguide pointing toward the interior of the chamber being covered with a porous layer.