A model based control procedure for the shape of a Nd:YAG cylindrical bar grown by edge-defined film-fed growth (E.F.G.) method when the pressure in the furnace oscillates
by
Liliana Braescu
Department of Mathematics, Polytechnical University of Timisoara, P-ta Regina Maria, No.1, 300004 - Timisoara, Romania
Coauthors: Agneta M. Balint (Department of Physics, The West University of Timisoara), Stefan Balint (Department of Mathematics, The West University of Timisoara)

The main purpose of this paper is to give a model based proof of the fact that the effect of the variations of the pressure p can be compensated by an adequate variation of the pulling rate v in order to assure a constant diameter of the Nd:YAG cylindrical bar, grown from the melt by E.F.G. method.

For that, using a nonlinear model, we find the pulling rate and the pressure couples for which the system of differential equations, which governs the evolution of the crystal radius r=r(t) and the meniscus height h=h(t) in the case of cylindrical bar, has asymptotically stable steady-state solution (r*, h*). By interpolation we find the dependences r*=r*(p, v), h*=h*(p, v) and the set S of those couples (p, v) for which r*(p, v)= rf, where rf is a desired radius.

Using the curves S we show that, if during the growth the pulling rate v and/or the pressure p are changed, then the crystal radius is changed too. For a given variation of the pressure, during the growth, we give a control procedure i.e. a procedure to change adequately the pulling rate in order to obtain a single crystal with the prescribed radius rf.

Date received: December 18, 2003

Copyright © 2003 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # cakt-18.