1. Institute of High Current Electronics, Siberian Branch, Russian Academy of Sciences, 2/3 Akademichesky Ave., Tomsk 634055, Russia
2. Joint Institute for High Temperatures of the Russian Academy of Sciences, 13 Izhorskaya St., Bd. 2, Moscow 125412, Russia
3. National Research Nuclear University MEPhI, 31 Kashirskoe shosse, Moscow 115409, Russia