• A.V. Savilov, I.V. Bandurkin, V.L. Bratman, N.Yu. Peskov
  IAP/RAS, Nizhny Novgorod
• A.K. Kaminsky, S.N. Sedykh
  JINR, Dubna, Moscow Region

Various schemes of THz electron masers operating in the regime of frequency multiplication are discussed. The use of this approach makes possible the realization of high-harmonic cyclotron masers operating at low (tens kV) accelerating voltages in long-pulse and CW regimes with the relatively low (1W-1kW) output power. Our first modeling experiment has demonstrated co-generation of second and fourth cyclotron harmonics in a simple microwave system. As for realization of pulsed high-power THz masers, it is attractive to use the regime of frequency multiplication in moderately-relativistic (hundreds kV) high-current FEMs and Smith-Purcell autooscillators. In our experiment based on a 0.8MeV/200A e-beam, a two-wave FEM was realized. In this experiment, the low-frequency (30GHz) wave was excited in the ubitron regime, and a feedback system partially reflected this wave back to the operating cavity. This backward low-frequency wave was scattered on the electrons into the forward high-frequency (360GHz) wave. The use of the regime of frequency multiplication provided the stimulated character of this process, and, therefore, a quite high power (~100kW) of the high-frequency wave.