To investigate purification process of silicon by heating, melting and evaporation dynamics, Laser Doppler Anemmometry (LDA) and Laser Doppler Granulometry (LDG) have been
used, deep inside R.F. plasma torch, despite temperature and extreme physical conditions in this medium. The process observed in flight were characterized through : particle rate, particle velocity, as well as particles size. When silicon particles get through the torch, they undergo rapid heating and melt into droplets, part of the liquid mass is evaporated proportionally to the surface of molten particles while the impurities concentrated on the surface are eliminated by evaporation.