Excitation Temperature Measurements on a New Atmospheric Microwave Plasma Torch

In this work, we present the results of a new approach of atmospheric microwave plasma torch (MPT), measuring the excitation temperature of the plasma. The new system consists of a cylindrical resonant cavity and a microwave source, a magnetron operating at a frequency of 2.45 GHz and power of 880 W, which is used to generate plasma inside a quartz tube, mounted coaxially along the cavity, with a diameter of 7 mm. The cylindrical cavity excites a dominant electric transverse mode TE111, in which surface waves transporting energy reach up to levels of 100 W/m3sr. The magnetron generator converts the input energy into plasma, in which the absorbed power is the result of the balance between the incident power and reflected power, but it depends on source losses in the cavity, the connection of the cavity, and the existence of other microwave harmonics. We use the optical emission spectroscopy to measure the excitation temperature, determined by Boltzmann plot method, based on the detection of several plasma emission lines, resulting in an excitation temperature of (3400 ±500)K.