Pankratev, Yu.I.; Naboka, V.A.; Ponomarenko, E.F.; Lavrentev, O.A.; Pankratev, Yu.I.; Physico-Technical Institute of the Ukrainian Academy of Sciences, Kharkov, Union of Soviet Socialist Republics; Naboka, V.A.; Physico-Technical Institute of the Ukrainian Academy of Sciences, Kharkov, Union of Soviet Socialist Republics; Ponomarenko, E.F.; Physico-Technical Institute of the Ukrainian Academy of Sciences, Kharkov, Union of Soviet Socialist Republics; Lavrentev, O.A.; Physico-Technical Institute of the Ukrainian Academy of Sciences, Kharkov, Union of Soviet Socialist Republics