Ultrashort pulse generation based on two coupled helical gyro-TWTs M.N. Vilkov, N.S. Ginzburg, G.G. Denisov, I.V. Zotova, A.S. Sergeev, A.M. Malkin, S.V. Samsonov and S.V. Mishakin EPJ Web Conf., 149 (2017) 04041 Published online: 04 August 2017 DOI: 10.1051/epjconf/201714904041