[1] NSC Kharkov Inst Phys & Technol, Inst Plasma Phys, Kharkov, Ukraine
[2] Karlsruhe Inst Technol KIT, IHM, D-76344 Karlsruhe, Germany
[3] Kharkov Polytech Inst, NTU, UA-61002 Kharkov, Ukraine
[4] Andrzej Soltan Inst Nucl Studies IPJ, PL-05400 Otwock, Poland
[5] Forschungszentrum Julich, IEF, D-52425 Julich, Germany