1. Department of Physics, York Plasma Institute, University of York, Heslington, York YO10 5DD, United Kingdom
2. Research Group for Biomedical Plasma Technology, Ruhr-Universität Bochum, Universitätsstraße 150, 44801 Bochum, Germany
3. Institute of Electrical Engineering and Plasma Technology, Ruhr-Universität Bochum, Universitätsstraße 150, 44801 Bochum, Germany
4. Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 2601, Australia