1. Department of Electronics, TEI of Crete, Chania 73133, Crete, Greece
2. Center for Plasma Physics and Lasers, TEI of Crete, Chania 73133, Crete, Greece
3. School of Nuclear Engineering, Purdue University, West Lafayette, IN 47907, USA
4. NSSE, NIE, Nanyang Technological University, Singapore 637616, Singapore