| AVS 55th International Symposium & Exhibition | |
| Plasma Science and Technology | Tuesday Sessions |
| Session PS-TuP |
| Session: | Plasma Science Poster Session |
| Presenter: | K. Niemi, Queen's University Belfast, Northern Ireland |
| Authors: | J. Waskoenig, Queen's University Belfast, Northern Ireland K. Niemi, Queen's University Belfast, Northern Ireland T. Gans, Queen's University Belfast, Northern Ireland |
| Correspondent: | Click to Email |
Atmospheric pressure plasmas in particular micro-discharge devices have tremendous application potential and are already used and targeted for a variety of technological and bio-medical applications. Micro-atmospheric pressure plasma jets (μ-APPJs) can provide high concentrations of radicals at a low gas temperature, particularly for modification of sensitive surfaces, such as in biomedicine or for surface coatings. Nevertheless the fundamentals of these non-equilibrium plasmas at ambient pressure are only rudimentarily understood. In general, the diagnostics of atmospheric pressure plasmas is extremely challenging, therefore numerical simulations offer a further insight into these discharges. The presented 1D-model is a numerical fluid-model along/across the discharge gap for a μ-APPJ. Dual frequency (2f) excitation of the μ-APPJ promises enhanced efficiency concerning the radical production and additional control for the plasma production. The discharge dynamics of the 2f excitation is investigated in various parameter ranges. Modelling and numerical simulations are however mainly restricted due to the lack of available data, particularly for surface processes which are crucial at these small dimensions because of the extraordinary high surface to volume ratios. Using experimentally measurable quantities as fixed input parameters of the model offers the opportunity to overcome this lack of available data. The μ-APPJ has been specially designed to provide an excellent optical diagnostic access to the discharge volume. Absolute atomic radical densities can be measured using two-photon absorption laser-induced fluorescence spectroscopy for use as a fixed input parameter in the model. Absolute measurements require detailed knowledge of collisonless de-excitation processes in particular under atmospheric pressure conditions. This can be obtained from the effective fluorescence decay rate (estimated lifetime of about 100 ps). The required temporal resolution can be achieved using a tuneable UV Fourier-limited picosecond laser system (1 cm-1, 10 ps). Within the simulation the sticking coefficient for atomic oxygen loss at the electrode surfaces is varied until consistency with the locally measured atomic oxygen ground state density is reached.