A.I. Benedik - Post-graduate Student, Engineer, Saratov State University named after N.G. Chernyshevsky. E-mail: andrej-benedik@yandex.ru A.G. Rozhnev - Senior Research Scientist, Saratov State University named after N.G. Chernyshevsky. E-mail: RozhnevAG@info.sgu.ru N.M. Ryskin - Dr. Sc. (Phys.-Math.), Professor, Head of Department, Saratov State University named after N.G. Chernyshevsky, Senior Research Scientist, Saratov branch of Kotel\'nikov IRE of RAS. E-mail: RyskinNM@info.sgu.ru N.I. Sinitsyn - Dr. Sc. (Phys.-Math.), Deputy Director, Saratov branch of Kotel\'nikov IRE of RAS. E-mail: SinitsynNI@gmail.com G.V. Torgashov - Ph. D. (Phys.-Math.), Head of Laboratory, Saratov branch of Kotel\'nikov IRE of RAS. E-mail: TorgashovGV@gmail.com P.D. Shalaev - Ph. D. (Eng.), Head of Department, JSC «SPE «Almaz» (Saratov). E-mail: p.d.shalaev@yandex.ru