Powerful Cherenkov Masers with 2D Slow-wave Structures of Planar and Cylindrical Geometry

Spatially-extended high-power Cherenkov masers operating in millimeter wavelength band intended for using in powering systems of Compton-type FELs are under development in collaboration of IAP RAS (Nizhny Novgorod) and BINP RAS (Novosibirsk). Electrodynamic systems of such oscillators are based on 2D periodical slow-wave structures realizing 2D distributed feedback mechanism, allowing for provision of stable narrow-band oscillation regime under conditions of substantial oversize. This novel feedback mechanism is examined for the oscillators of different geometry.Project of Ka-band Cherenkov Surface-Wave Oscillator of sub-GW power level is elaborated based on high-current explosive-emission accelerator “Sinus-6” 0.5MeV/5kA/20ns (IAP RAS) forming relativistic electron beam of a tubular geometry with diameter of about 40mm. To ensure high-coherence of the radiation from the large-size beam, we exploit cylindrical slow-wave structure with 2D doubly-periodical corrugation. In the proof-of-principal experiments under the transverse oversize parameter of the system (perimeter to the wavelength) of about 16, the narrow-band oscillations was obtained with the power level of $\sim 0.25-0.3 \mathrm{GW}$. Optimization of parameters aimed at further power enhancement is in progress currently.Project of powerful W-band Cherenkov maser of planar geometry is under development in collaboration between IAP RAS and BINP RAS at the “ELMI” accelerator. This accelerator forms electron beam 1MeV/5–7kA$/ 3 \mu \mathrm{s}$ of sheet geometry with the transverse cross-section of 0.3cm $\times18$ cm. In present paper, design parameters of this project are discussed and results of the simulations are presented, which demonstrate possibility to achieve in the considered scheme a stable narrow-band oscillation regime with output power of the GW-level under the transverse oversize parameter (width to the wavelength) of up to 50. Experiments on realization of this super-power Cerenkov maser are started.