1. Russian Research Centre ‘Kurchatov Institute’, Nuclear Fusion Institute, 123182 Moscow, Russia
2. Laboratorio Nacional de Fusión por Confinamiento Magnético Asociación EURATOM-CIEMAT, 28040-Madrid, Spain
3. National Science Center, Kharkov Institute of Physics and Technology, Institute of Plasma Physics, NSC KIPT 61108 Kharkov, Ukraine
4. A. F. Ioffe Physical-Technical Institute, St. Petersburg, Russia