1. Department of Radiation Dosimetry , Nuclear Physics Institute of the Czech Academy of Sciences, 180 00 Prague , Czech Republic
2. Czech Technical University in Prague , Faculty of Nuclear Sciences and Physical Engineering, 115 19 Prague , Czech Republic
3. Czech Technical University in Prague , Faculty of Electrical Engineering, 160 00 Prague , Czech Republic
4. Brno University of Technology , Faculty of Electrical Engineering and Communication, 601 90 Brno , Czech Republic