This is an early access version, the complete PDF, HTML, and XML versions will be available soon. Open AccessArticle by Ondrej Kovarik 1,*, Jan Cizek 2 and Jakub Klecka 1,2 1 Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Trojanova 13, 120 00 Prague 2, Czech Republic 2 Institute of Plasma Physics of the Czech Academy of Sciences, Za Slovankou 1782/3, 182 00 Prague 8, Czech Republic * Author to whom correspondence should be addressed.