1. School of Physics, Free University of Tbilisi, Tbilisi 0159, Georgia
2. Andronikashvili Institute of Physics (TSU), Tbilisi 0177, Georgia
3. E. Kharadze Georgian National Astrophysical Observatory, Abastumani 0301, Georgia
4. Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712, USA