Numerical simulations of a RF-RF hybrid plasma torch with argon at atmospheric pressure

We report numerical results regarding the minimum sustaining coil excitation current for a RF-RF hybrid torch operating at two different frequencies. The first coil is excited at a high-frequency, while the second coil is set at a medium frequency. The filling gas is argon, at atmospheric pressure. We use the modeling software COMSOL Multiphysics to describe the evolution of key parameters when: (i) the distance between the two coils changes, (ii) the power of the high frequency coil changes. We discuss the radial temperature profiles, the axial velocities and the heat convected at the end of the medium-frequency coil. The latter is compared with the total heat conduction to the plasma confinement tube wall.