1. H. Niewodniczański Institute of Nuclear Physics, Radzikowskiego 152, 31-342 Kraków, Poland
2. Mining Academy, Mickiewicza 30, 30-059 Kraków, Poland
3. M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków, Poland
4. Institutt for energiteknikk, 2007 Kjeller, Norway