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Novel schemes of powerful multichannel planar FEMs was developed based on two parallel sheet beams 0.8 MeV / 1 kA forming by the accelerator ELMI. In 75 GHz frequency band two-channel planar FEM operating with two-dimensional distributed feedback was elaborated. For record transverse size of interaction space (up to 45 × 2.5 wavelengths) synchronization of emission from both electron beams and realization...
Ka-band surface wave oscillator of a cylindrical geometry driven by tubular electron beam 300 keV / 100 A / 3 μs has been realized. Narrow-band regime of oscillations in strongly oversized system (perimeter-to-wavelength ratio is about 16) was achieved using periodical structure with two-dimensional corrugation. Output power of 1.5–2 MW level was obtained. High stability of the oscillation frequency...
The paper describes recent results of theoretical and experimental studies of powerful relativistic masers based on linac LIU-3000. The key components of the oscillators are advanced Bragg resonators based on coupling of propagating and quasi-cutoff waves that possess high selectivity over transverse coordinates and allows establishment of narrow-band operating regime in strongly oversized system...
Powerful high-efficiency FEM-amplifier operating over Ka frequency range and aimed on accelerating applications is developed in collaboration between IAP RAS and JINR. To achieve a broad amplification band in a regular wiggler, we utilized the so-called grazing regime, in which about of 20 MW of output power was simulated in the frequency range of 30 ± 3 GHz. In the first stage of experiments, the...
The paper describes recent results of theoretical and experimental studies of the FEM-oscillator driven by linac LIU-3000 0.8 MeV / 200 A / 200 ns. At the present stage efficient operation of the JINR-IAP FEM has been demonstrated at 30 GHz / 15 MW and 60 GHz / 5 MW powers. Project of multimegawatt power 90 GHz FEM is in progress currently. The key components of the FEM are short period tapered wiggler,...
Project of powerful FEM operating from Ka- to W-band and aimed to accelerating applications is developed in collaboration between JINR (Dubna) and IAP RAS (N. Novgorod) based on linac LIU-3000. The key components to advance the JINR-IAP FEM into short wavelengths are short-period tapered wiggler, which is responsible for high-quality helical electron beam formation, and advanced Bragg resonator with...
Possibility of JINR-IAP FEL driven by linac LIU-3000 to operate at THz frequency band has been studied. Present paper describes recent design of the oscillator and results of simulations for key elements of the oscillator, such as RF-undulator and Bragg resonator with quasi-cutoff feedback wave.
High-efficiency narrow-band 30-GHz Bragg FEM-oscillator was elaborated during the last few years in JINR-IAP collaboration based on 0.8 MeV / 200 A / 250 ns LINAC LIU-3000 (JINR). An attractive solution to prospect FEM into short wave-lengths keeping beam energy and geometry of electron-optical system is operation at harmonics of bounce-frequency. Two FEM schemes exploiting this idea are under development...
Employment of periodical Bragg structures can be considered as an effective way of controlling the electromagnetic energy fluxes and provision of spatial coherence of radiation in electron and optical devices with oversized interaction space. In the paper new modifications of Bragg structures are discussed that can be beneficial for drastic increasing of radiation power of mm and submm FELs and infrared...
A project to generate powerful sub-rom pulses in JINR-IAP FEM-oscillator driven by 08 MeV/200 A linac is in progress. This project is based on successful experiments at mm-wavelength band. To achieve sub-mm generation in the Bragg FEM we propose a two-wave interaction where the backward propagating (feedback) mm-wave would be used as a secondary wiggler and would scatter at a harmonic frequency into...
The generation of high power microwave radiation from a two-dimensional (2D) Bragg coaxial Free Electron Maser (FEM) is reported. Two 2D Bragg structures positioned at the input and output of an oversized co-axial interaction region were used to define the cavity of the FEM. Measurements of the transmission coefficient of the 2D Bragg structures were conducted and experimental results compared with...
This paper presents the results of experimental investigation on spectrum of powerful 4-mm pulses generated by a planar free electron maser with a hybrid resonator and an optimized wave deflector at the ELMI-device. The measured spectrum of the radiation is in accord with the results of computer simulations and ≪cold≫ measurements of the resonator spectral properties.
In the paper FEM oscillator operation based on coupling of quasi cut-off mode with propagating wave which is amplified by the electron is considered. The coupling is realized by periodical corrugation of side wall of microwave system. The cut-off mode provides the feedback while the efficiency in steady-state regime of generation is almost completely determined by the propagating mode, synchronous...
The paper is devoted to progress in development and application of the JINR-IAP FEM. This Bragg FEM generates 30 GHz pulses of up to 200 ns duration and 20–30 MW power with an efficiency on the level of ∼25 %. Frequency tuning in the range of 6 % with a precision of about 0.1 % was realized by mechanical variation of the distance between the Bragg reflectors. A test facility to study surface heating...
Theoretical and numerical considerations have shown that a planar FEM with 2-D distributed feedback is suitable to be used as a module for constructing multichannel devices to produce microwave radiation of GW level. Computer simulations for operation of 4-modules FEM-generator have demonstrated a perfect synchronization of all modules even at a little bit different energies of the electron beams...
The novel scheme of separation of the mm-wave radiation from the intense electron beam using planar Bragg wave transformer, is suggested and realized. In the experiments at the planar FEM with the new scheme of separation, the generation of powerful 4-mm radiation pulses was observed. The duration of these pulses is increased in two times in comparison with the old scheme of the beam dump and has...
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