[1] Kazimierz Wielki Univ Bydgoszcz, Inst Phys, PL-85090 Bydgoszcz, Poland
[2] Ivan Franko Natl Univ Lviv, Dept Elect, UA-79017 Lvov, Ukraine
[3] Inst Scintillat Mat NAS Ukraine, UA-6100 Kharkov, Ukraine
[4] Inst Phys AS Czech Republ, Prague 16253, Czech Republic
[5] Charles Univ Prague, Fac Math & Phys, Pragu 12116, Czech Republic