Two-stream Superheterodyne Free Electron Lasers Research Articles

MULTIPLE THREE-WAWE RESONANCES IN TWO-STREAM FREE-ELECTRON LASER WITH A HELICAL ELECTRON BEAM

Background. A powerful terahertz radiation sources creation is one of the perspective tendencies in relativistic plasma electronics. Nowadays there are few devices able to create powerful radiation in millimeter-infrared waveband (even in the part of this band). Therefore, theoretical research of novel powerful terahertz radiation sources, that are also characterized by broad frequency spectrum, is an actual problem.Objective. The aim of the paper is a study of the influence of multiple three-wave resonant interactions in the klystron type two-stream superheterodyne free-electron laser (TSFEL) with helical electron beam on the forming effectiveness of the powerful waves with broad frequency spectrum.Methods. In order to theoretically analyze multiple resonances of wave harmonics, as initial, we use quasihydrodynamic equation, the continuity equation and Maxwell’s equations. We apply the hierarchic approach to the theory of oscillations and waves to the equations of motion and continuity, Maxwell’s equations are solved by means of the slowly varying amplitudemethod. As a result, we derive a system of differential equations for complex amplitudes of SCW electric field strength harmonics which we analyze by standard methods.Results. It was shown that in the two-stream superheterodyne FELs, utilizing the two-stream instability in helical electron beams as an additional electromagnetic wave amplification mechanism, the powerful multiharmonic space charge wavewith broad frequency spectrum forms due to multiple resonant interactions. The spectrum width of such wave is larger compared to the spectrum width in TSFELs utilizing straight electron beams. It is also found out that amplification rates in such TSFELs are higher.Conclusions. An application of helical electron beams in multiharmonic TSFELs using multiple resonant interactions leads to the improvement of their amplification characteristics, frequency spectrum widening in multiharmonic signal generation mode, and to overall geometric dimensions decreasing compared to TSFELs utilizing straight beams.Keywords: two-stream superheterodyne free-electron laser; two-stream instability; helical electron beams; three-wave resonances.

Influence of two-stream relativistic electron beam parameters on the space-charge wave with broad frequency spectrum formation

We developed a cubic non-linear theory describing the dynamics of the multiharmonic space-charge wave (SCW), with harmonics frequencies smaller than the two-stream instability critical frequency, with different relativistic electron beam (REB) parameters. The self-consistent differential equation system for multiharmonic SCW harmonic amplitudes was elaborated in a cubic non-linear approximation. This system considers plural three-wave parametric resonant interactions between wave harmonics and the two-stream instability effect. Different REB parameters such as the input angle with respect to focusing magnetic field, the average relativistic factor value, difference of partial relativistic factors, and plasma frequency of partial beams were investigated regarding their influence on the frequency spectrum width and multiharmonic SCW saturation levels. We suggested ways in which the multiharmonic SCW frequency spectrum widths could be increased in order to use them in multiharmonic two-stream superheterodyne free-electron lasers, with the main purpose of forming a powerful multiharmonic electromagnetic wave.

Plural Interactions of Waves in Multiharmonic Two-stream Superheterodyne Free-electron Lasers with Helical Electron Beams

Plural Interactions of Waves in Multiharmonic Two-stream Superheterodyne Free-electron Lasers with Helical Electron Beams

Forming of Space Charge Wave with Broad Frequency Spectrum in Helical Relativistic Two-Stream Electron Beams**Supported by the Ministry of Education and Science of Ukraine under Grant No 0117U002253.

We elaborate a quadratic nonlinear theory of plural interactions of growing space charge wave (SCW) harmonics during the development of the two-stream instability in helical relativistic electron beams. It is found that in helical two-stream electron beams the growth rate of the two-stream instability increases with the beam entrance angle. An SCW with the broad frequency spectrum, in which higher harmonics have higher amplitudes, forms when the frequency of the first SCW harmonic is much less than the critical frequency of the two-stream instability. For helical electron beams the spectrum expands with the increase of the beam entrance angle. Moreover, we obtain that utilizing helical electron beams in multiharmonic two-stream superheterodyne free-electron lasers leads to the improvement of their amplification characteristics, the frequency spectrum broadening in multiharmonic signal generation mode, and the reduction of the overall system dimensions.

Forming of Ultrashort Electromagnetic Clusters by Two-Stream Superheterodyne Free Electron Lasers

Forming of Ultrashort Electromagnetic Clusters by Two-Stream Superheterodyne Free Electron Lasers

The project of the compact media-accelerator for the two-stream superheterodyne free electron laser

The results concerning the project of compact two-stream superheterodyne free electron lasers, which can be constructed on the basis of MLIA-accelerator, are represented. In the work is described the nonlinear theory of the multi-harmonic TSFELs and accomplished corresponding physical and project analysis. A specific characteristic of the considered system is the source of intensive relativistic electron beam is constructed on the basis of a two-beam MLIA-accelerator. The design-scheme of the compact MLIA-accelerator is proposed and analyzed. It is shown that main merit of studied devices is their potential compactness.

THE TWO-STREAM MULTI-HARMONIC FEL AS A POWERFUL SOURCE OF FEMTO-SECOND WAVE PACKAGES

A possibility to construct a powerful source of femto-second wave packages is analyzed. The method as well as design variant of the system for forming such packages (the multi-harmonic two-stream superheterodyne free electron laser - MTSFEL) are proposed. It is shown that very short packages (units– tens femto-second) can be obtained in the case, when the frequency of the input monochromatic (transforming) signal is much less than the optimal frequency for two-stream instability.

Two-Stream Free Electron Lasers: Physical and Project Analysis of the Multiharmonical Models

The multi-harmonic models of two-stream superheterodyne free electron lasers (TSFELs) are proposed and analyzed. It is shown that such systems can have a number of unique features. Including, they are the generation of signals with complex multi-harmonic spectrum, amplification of complex multi-harmonic signals with small distortions, etc. The nonlinear theory of the multi-harmonic TSFELs is constructed and analyzes of two possible projects for their experimental realization is accomplished.

Two-Stream Free Electron Lasers: Physical Analysis of the Systems with Monochromatic Pumping

Nonlinear selfconsistent theory of the Two-stream Superheterodyne Free Electron Lasers (TSFELs) is represented. The one-sectional and klystron type models of TSFEL-amplifiers are analyzed. It is shown that such systems can provide extremely high levels of amplification, and, at the same time, high levels of the input-output decoupling.

Two-Stream Free Electron Lasers: General Properties

Some general properties of the Two-stream Superheterodyne Free electron Lasers (TSFELs) as a new class of relativistic electronic devices have been studied. Including, their operation principles, design schemas, and peculiarities of mathematical description have been discussed.