The new generation of microwave powerheads, generators and tuning elements enable compact plasma sources at atmospheric pressure (APS) for surface and volume treatment. The APS is such an atmospheric plasma source based on a special designed microwave cavity. Microwaves with a frequency of 2.45 GHz are fed into the plasma source resulting in a high field concentration in the middle of the cavity.
In this region, the plasma is ignited and heated. Several kilowatts can be injected into the plasma and gas temperatures up to 3500 K can be determined with optical emission spectroscopy methods. The APS is well suited for the removal of very dilute concentrations of air pollutants such as volatile organic compounds (VOC) and their fluorinated derivates (FOC), for the synthesis of special gases and for the production of nanoparticles.
Scalable plasma sources are required for energy-efficient and resource-saving high rate processes in plasma chemistry and plasma-based coating technology in order to meet industrial requirements. The 915 MHz plasma torch is the high-performance version of the microwave torch up to 100 KW. For air plasmas it has the typical values of 4000 K for the neutral gas temperature and 6000 K for the electron temperature at electron densities of 1020 m-3.