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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...
We demonstrate that gyrotrons operating in the regime of developed turbulence can sporadically emit “giant” spikes with intensities a factor of 100 ÷ 200 greater than the average radiation power and a factor of 4 ÷ 6 exceeding the power of a driving electron beam. Together with a long-tail pulse-height probability distribution, this allows the interpretation of generated spikes as microwave rogue...
The possibility of generation of high-power (multi-megawatt) broadband terahertz radiation during stimulated backscattering of an intense millimeter-wavelength pump wave by a high-current reletivistic electron beam (REB) is shown. With allowance for a significant parameter spread that is typical for high-current REBs, the kinetic interaction regime is expedient, This regime leads to the broadening...
A periodic train of powerful ultrashort microwave pulses can be generated in electron oscillators with a saturable absorber installed in the feedback loop. This method of pulse formation is similar to the passive mode-locking widely used in laser physics where such pulses are also treated as dissipative solitons. We consider the method of mode-locking applied to different types of microwave amplifiers...
A double-beam scheme of a short-wavelength gyrotron operating at the second cyclotron harmonic is studied both within the framework of the averaged self-consistent approach and using 3-D particle in cell simulations. The analysis shows that the introduction of an additional generating electron beam allows drastically increasing the operating current of a second-harmonic gyrotron with the simultaneous...
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.
We suggest to use the effect of cyclotron resonance absorption for modulation of microwave signals. Stationary signal transforms into the sequence of soliton-like pulses during interaction with rectilinear electron beam. For operating frequency of 250 GHz output pulses can possess subnanosecond durations.
Possibility of generation of multi-megawatt terahertz pulses based on undulator and Cherenkov mechanisms of superradiance from electron bunches formed by photo injection guns has been studied. Theoretical analysis was performed in the frame of average approach and confirmed by direct PIC simulations.
Within the frame of quasi-optical approach we develop a nonlinear theory of relativistic surface wave oscillators. Our theory provides a possibility to describe both linear and nonlinear stages of formation of evanescent slow-wave structure and include evaluation of threshold conditions, electron efficiency and output power.
Recently a significant progress has been achieved in generation of electromagnetic pulses in centimeter and millimeter waveband based on superradiance (SR) from high-current extended electron bunches formed by explosive emission cathodes [1]. Generated pulses are characterized by record-breaking (gigawatt) peak power and ultra-short (subnanosecond) duration. At particle energies up to 300 keV, current...
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...
Formation of standing solitons under cyclotron resonance interaction with backward rectilinear electron beam is described. In difference with photo-induced transparency in optics stopping occurs in the frame of more simple single photon process (e.g. in the absence of pump wave).
For increasing the integral power of short wavelength gyrotrons it is suggested to use the planar geometry of interaction space with a sheet electron beam and transverse (with respect to electron translation velocity) energy extraction. The advantage of such a scheme in comparison with conventional cylindrical gyrotrons is diffraction mode selection over the open transverse coordinate in combination...
We develop a quasi-optical theory of relativistic surface wave oscillator. The feasibility of generation of powerful submillimeter radiation in the considered type of devices is demonstrated.
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...
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...
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