1. Southwestern Institute of Physics, Chengdu 610041, China
2. National Institute for Fusion Science, Toki 509-5292, Japan
3. ITER Diagnostic Team, IO, Route de Vinon sur Verdon, 13115 St Paul lez Durance, France
4. FOM-Institute for Plasma physics “Rijnhuizen,” Association EURATOM, Trilateral Euregio Cluster, 3430 BE Nieuwegein, The Netherlands