C. Lazarou1,2, L. Wang3, A. Nikiforov3, C. Leys3, C. Anastassiou1,2, I. Topala4, A. S. Chiper4, I. Mihaila5, V. Pohoata4, P. Vogel6, A. Knodel6, B. Gilbert Lopez7, J. F. Garcia Reyes7, A. Molina-Diaz7, J. Franzke6 and G. E. Georghiou1,2 1 FOSS Research Centre for Sustainable Energy, Department of Electrical and Computer Engineering, University of Cyprus 2 ENAL Electromagnetics and Novel Applications Lab, Department of Electrical and Computer Engineering, University of Cyprus 3Department of Applied Physics, Ghent University, Belgium 4 Iasi Plasma Advanced Research Center (IPARC), Faculty of Physics, Alexandru Ioan Cuza University of Iasi 5 Integrated Center of Environmental Science Studies in the North-Eastern Development Region (CERNESIM), Alexandru Ioan Cuza University of Iasi 6ISAS—Leibniz Institut für Analytische Wissenschaften, Dortmund, Germany 7Analytical Chemistry Research Group, Department of Physical and Analytical Chemistry, University of Jaén (corresponding author email: lazarou.constantinos@ucy.ac.cy) • In this study, a two-dimensional axi-symmetric model has been developed to provide insight into the evolution of capillary helium plasma jet with and without the presence of oxygen admixtures and its interaction with a dielectric surface placed normal to the jet axis. • The model considers the gas mixing of helium and ambient air and the analytical chemistry between helium, nitrogen and oxygen species. • Experiments were performed in similar conditions as the simulations in order to get qualitative agreement between them. Understanding the evolution of a He and He/O2 capillary plasma jet This project has received funding from the European Union’s Horizon 2020 research and innovation programme under agreement No. 810686 Experimental Setup Results Acknowledgment Conclusions Introduction Theory and methodology Simulation domain • The gas dynamic model (GDM) is used to describe the flow of the helium jet in the ambient air [1]. The calculated profiles of the helium and air mole fraction and the mass average velocity are then fed into plasma fluid model (PFM). • The PFM uses the continuity equation in the drift diffusion approximation for the description of electrons and electron energy, and the multi-component diffusion equation for the description of the heavy species in the mixture (neutral, excited and ion species) [2]. • The equations of the PFM are coupled with the Poisson equation for the description of the electric field. Experimental Results Simulation Results Figure 1: Spatio-temporal evolution of the plasma bullet for (a) He and (b) He+O2 (1000 ppm) plasma jet. Time 0 ns corresponds to the plasma bullet just about the exit of the tube. The three dashed lines indicate the axial distance from the tube nozzle for z=0, 1 and 2 mm. Figure 2: Simulation results for the spatio-temporal evolution of the total ionization rate for (a) He and (b) He+O2 (1000 ppm) plasma jet. Time 0 ns corresponds to the plasma bullet just about the exit of the tube. The total ionization rate has units of mol/m3s. Figure 3: Simulation results of electron production rate in logarithmic scale for the He plasma jet. The plasma bullet is located at -0.75 mm from the tube exit. • The addition of oxygen admixtures in the helium gas promotes plasma bullet propagation on the axis of symmetry of the tube (instead off axis propagation for the pure helium plasma jet). • The simulation results show that the shape of the plasma bullet during its propagation is controlled by the generation of seed electrons in front of the streamer head. • For He/O2 plasma jets, the shape of the bullet remains sphere like because the seed electrons are mainly produced uniformly along the axis of symmetry in the helium channel, through Penning ionization of helium metastable species with the admixture of O2 molecules. • For the pure helium jet the bullet is torus shaped because seed electrons in the helium channel are mainly generated on the edges of the channel through