Laser diagnostics on atmospheric pressure plasma jets

Atmospheric pressure plasma jets (APPJs) are plasmas produced at an electrode inserted in a tube through which a gas is blown. They are characterized by their small size and their non-equilibruim state, which means that in an APPJ the electron temperature is much higher than the gas temperature. Thee energetic electrons and the high particle densities at atmospheric pressure make that an APPJ has a complex chemistry, in which all kinds of reactive species are produced, for example atomic oxygen (O) and nitrogen (N), OH, NO and O3. The combination of the rich electron-driven chemistry and low gas temperature makes that APPJs are useful for applications, such as the treatment of (heat sensitive) surfaces, or biomedical applications such as decontamination and wound-healing. An additional advantage is that the jet allows for remote plasma treatment. In this thesis three different sources are used, which cover a large range of plasma parameters, such as electron densities and gas temperatures. The sources —a surfatron launcher, a coaxial microwave jet and a radio frequency (RF) jet—differ in electrode configuration, driving frequency (RF or microwave), and gas composition (helium or argon with various amounts of pre-mixed air, O2 or N2). The jets are operated in an ambient air environment resembling the applications conditions, and are subject to the entrainment of air into the jet. The main benefit of APPJs—the rich chemistry—is at the same time the biggest challenge in research, and with the current status of the modeling efforts, experimental data is still the most reliable source of information. The goal of this thesis is therefore to provide experimental data to help understanding the plasma chemistry in APPJs. This puts high demands on the diagnostics, which have to be non-intrusive, in situ with a high spatial resolution, and able to cope with the high collision rates typical for atmospheric pressure plasmas. The diagnostics best suited to achieve this are spectroscopic methods. Various spectroscopic ...