The effect of the gas flow-rate on the radial structure of a torch-like helium plasma

The effect of the gas flow-rate on the radial structure of a torch-like helium microwave plasma has been studied by measuring the radial distributions of emission intensity of spectral lines from helium and from the air that surrounds the discharge. It has been found that increasing the gas flow-rate leads to an increase of the maximum of the spectral lines and a shift of these emission peaks toward the plasma edge. Apart from that, it is found that the entrainment of air into the plasma increases with the flow-rate.