General electromagnetic model of active plasma resonance spectroscopy and its application to spatiotemporal electron density and temperature measurements of nanodusty plasmas

• Applicants: Privatdozent Dr. Franko Greiner; Professor Dr.-Ing. Jens Oberrath
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 531667910

Microwave methods are excellent for non-invasive diagnostics of plasmas. Compared to classical interferometry, methods that exploit the cavity resonances of plasma chambers (cavities) are very sensitive and can be used up to electron densities of 10^7 m^(-3). With the mathematical methods and microwave measurement techniques available today, methods can be devised that allow spatially resolved electron density measurements and their experimental verification. The detailed simulation of real cavities with a number of microwave receiving and transmitting antennas also allows the determination of the electron temperature. In this project a microwave resonance spectroscopy is developed, which allows arbitrarily shaped cavities and enables the spatially resolved determination of the electron density. To determine the electron temperature, the accurate simulation of the real cavities is required to separate the broadening of the resonances due to the cavity quality from that due to temperature effects. The latter can be determined with the kinetic model of the method. From the models, diagnostic methods are developed that are applied to various low-temperature plasmas. For pure argon plasmas, the new microwave diagnostic can be compared with spatially resolved Langmuir probe measurements. In nanodusty plasmas, which contain nanoparticles as well as ions and electrons, the new diagnostic allows to test dust density wave diagnostics for the first time. Even for reactive, nanoparticle-generating plasmas, the new method can be applied to perform spatially resolved measurements of electron density during particle growth, which has not been possible before.

• DFG Programme: Research Grants
• Major Instrumentation: Vektornetzwerkanalysator
• Instrumentation Group: 2720 Impedanz- und Dämpfungsmeßgeräte, Frequenzgangmeßgeräte, Netzwerkanalysatoren