MODELING, PROJECT, NUMERICAL-SIMULATION, AND AES TEMPERATURE DIAGNOSTICS OF AN INDUCTIVELY-COUPLED PLASMA TORCH FOR THE DEPOSITION OF HIGH-PURITY FUSED-SILICA FOR OPTICAL WAVE-GUIDE PRODUCTION

An inductively coupled plasma torch has been designed for the synthesi s of high-purity, low-OH, fused silica in fiber optics preform product ion by means of a new technological process, within the framework of p lasma outside deposition, The torch, working at atmospheric pressure, is attached to a 13.56 MHz, 5.4 kW RF generator; system geometry, inle t gas velocities, heat exchange, and electrical coil configurations ha ve been selected in accordance with the physical modeling and numerica l simulation results, Temperature, velocity, and electromagnetic field s have been computed by using a two-dimensional (2-D) fluid-magnetic c ode assuming LTE for the plasma, A 2-D treatment of electromagnetic fi eld equations has been performed using boundary conditions, treating t he torch as a point magnetic dipole, within a grid extending outside t he plasma zone; results for the electric field in the torch will be pr esented in different steps of plasma initiation in test Ar discharges, Temperature diagnostics have been performed within atomic emission sp ectroscopy techniques: side-on experimental profiles have been treated through Abel inversion, Results obtained with the Boltzmann plot meth od (lateral and radial excitation temperature profiles) are presented, and conclusions are drawn concerning possible plasma deviations from LTE conditions, The first results on the deposition of soot silica wil l be described, together with torch operating conditions and reactive mixture O-2 + SiCl4 characteristics.