[1] Max Planck Inst Plasma Phys, D-85748 Garching, Germany
[2] ENEA, Fus & Nucl Safety Dept, Via Enrico Fermi 45 CP 65, I-00044 Frascati, Italy
[3] Swiss Plasma Ctr SPC, Ecole Polytech Fed Lausanne EPFL, CH-1015 Lausanne, Switzerland
[4] Zhejiang Univ, Inst Fus Theory & Simulat, Sch Phys, Hangzhou, Peoples R China