Influence of the nozzle head geometry on the energy flux of an atmospheric pressure plasma jet Thorben Kewitz, Christoph Regula, Maik Fröhlich, Jörg Ihde and Holger Kersten EPJ Techn Instrum, 8 1 (2021) 1 Published online: 07 January 2021 DOI: 10.1140/epjti/s40485-020-00061-4