Electron-optics systems with decreased life-time of trapped electrons for terahertz gyrotrons V.N. Manuilov, A.L. Goldenberg, M.Yu. Glyavin and K.A. Leshcheva EPJ Web Conf., 195 (2018) 01007 Published online: 23 November 2018 DOI: 10.1051/epjconf/201819501007