1. Institute of Plasma Physics of the CAS, Za Slovankou 1782/3, 182 00 Prague 8, Czech Republic
2. Institute of Physics of the CAS, Na Slovance 1999/2, 182 21 Prague 8, Czech Republic
3. Institute of Physics of the CAS, Cukrovarnicka 10/112, 162 00 Prague 6, Czech Republic
4. ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France