Plasma and nanoparticles in cylindrical microwave cavities

Low-pressure acetylene plasmas are able to spontaneously form (under certain conditions) dust particles, resulting in a cloud of charged particles up to micrometer sizes levitated in the plasma. A capacitively coupled plasma is ignited in a cylindrical discharge chamber that simultaneously serves as microwave resonator. Microwave cavity resonance spectroscopy (MCRS) is used to determine the electron density of the plasma. However, the accuracy of this method is directly influenced by the presence and abundance of the dust particles. This is studied in more detail by using multiple cavities. The spatial distribution of the dust is visualized with laser light scattering and video imaging thereof. The charge of the particles is also an important parameter in industrial plasma environments, where electromagnetic fields can be used to deflect or attract the particles. To gain more insight into the charging and discharging mechanisms, MCRS is complemented with other electrical measurements when the plasma is switched on and off, providing the important timescales related to these processes.