Analysis of Thermal Induction Plasmas between Coaxial Cylinders

A previously derived approximate solution of the one-dimensional energy-balance equation for steady thermal induction plasmas is applied to the case of an annular plasma contained between coaxial cylinders. It is assumed that heat conduction is the only loss mechanism and that both walls are at zero temperature. Charted material is presented to facilitate determination of heat loads to either wall and calculation of temperature distributions across the gap. Results for an atmospheric-pressure argon discharge are compared with both exact numerical calculations and with experimental data. With the former, agreement is fair to good; with the latter it is poor. The disagreement is shown to be caused by electron diffusion which leads to overpopulation near the walls and suggests erroneously high temperatures when Saha equilibrium is assumed. The experimental temperature profiles are reproduced with excellent accuracy from a diffusion profile for the electrons which takes into account the nonuniformity of the induced electric field.