Development of electron gun for miniaturized millimeter-band traveling-wave tube Dmitry A. Nozhkin1,2, Roman A. Torgashov1,2, Dmitry A. Bessonov1,3, Igor A. Navrotsky1,3, Nikita M. Ryskin1,2; 1Saratov Branch, Institute of Radio-Engineering of RAS, Saratov, Russia; 2Saratov State University, Saratov, Russia; 3 RPE “Almaz”,Saratov, Russia