• N.Yu. Peskov, N.S. Ginzburg, S.V. Kuzikov, A. Sergeev
  IAP/RAS, Nizhny Novgorod
• A.K. Kaminsky, E.A. Perelstein, S.N. Sedykh
  JINR, Dubna, Moscow Region

The JINR-IAP FEM-oscillator was elaborated during the last few years based on 0.8 MeV / 200 A / 250 ns linac LIU-3000 (Dubna). This 30-GHz FEM generates currently 20 MW / 200 ns pulses with spectrum width of ~6 MHz and repetition rate of up to 1 Hz. The high efficiency and stability of the FEM was achieved by using reversed guide magnetic field regime and advanced type of Bragg resonator, i.e. resonator with a step of phase of corrugation. The parameters achieved allow the FEM to be used in several applications. Test facility to study the life time of the metals in strong RF-fields was constructed based on the FEM. This information would be beneficial, in particular, when designing high-gradient accelerating structures for future linear colliders. Degradation of the copper surface was studied at different temperature rise during each pulse (from 50° to 250° C) in consequence of up to ~100 000 pulses. Investigation of possibility to use JINR-IAP FEM in medical and biological applications was also started. The effect of the powerful 30-GHz pulses on the biological tissue including the cancer cells was studied. Project to advance JINR-IAP FEM into sub-mm wavelengths is developed.

• 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.