1. Andronikashvili Institute of Physics, TSU, Tbilisi 0177, Georgia and Department of Physics, Faculty of Exact and Natural Sciences, Ivane Javakhishvili Tbilisi State University (TSU), Tbilisi 0179, Georgia
2. Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712, USA
3. Andronikashvili Institute of Physics, TSU, Tbilisi 0177, Georgia and School of Physics, Free University of Tbilisi, Tbilisi, Georgia