Characteristics of Microwave Plasma Torch at Atmospheric Pressure

We studied the characteristics of a microwave argon plasma torch at atmospheric pressure. The electron temperature of the plasma was measured by optical-emission spectroscopy and increases nonlinearly from 3000 to 3800 K with the increase of the microwave power from 1.0 to 4.0 kW. The spatial distribution of the electron density was measured with a Mach-Zehnder interferometer to be on the order of 10
¹⁷
/cm
³
and characterized by fluctuating with the time under the same experimental conditions. Based on the plasma parameters measured, it can be concluded that the plasma is in the state of local thermodynamic equilibrium.