Plural Three-Wave Resonant Interactions in the Transit Section of Two-Stream Superheterodyne FEL with a Longitudinal Electric Field

Authors A.V. Lysenko , I.I. Volk , G.A. Oleksiienko , M.A. Korovai , A.T. Shevchenko

Sumy State University, 2, Rymsky-Korsakov St., 40007 Sumy, Ukraine

Issue Volume 13, Year 2021, Number 4
Dates Received 10 June 2021; revised manuscript received 09 August 2021; published online 20 August 2021
Citation A.V. Lysenko, I.I. Volk, G.A. Oleksiienko, et al., J. Nano- Electron. Phys. 13 No 4, 04027 (2021)
PACS Number(s) 41.60.Cr, 52.59.Ye
Keywords Superheterodyne free-electron laser, Two-stream instability, Three-wave parametric resonance, Space charge wave, Longitudinal electric field.

In the present work, within the framework of nonlinear cubic approximation, the analysis of the possibility of controlling the parameters of a wide frequency spectrum in multiharmonic two-stream free-electron lasers of klystron type by means of a longitudinal electric field was carried out. The quasihydrodynamic equation, the continuity equation and Maxwell equations were used as the calculation basis. Using the method of averaged characteristics, we obtained a system of differential equations describing the dynamics of wave harmonics amplitudes of a superheterodyne free-electron laser. We demonstrated that in the studied system, it was possible to realize plural three-wave parametric resonances between space charge wave harmonics. In this case, simultaneous three-wave resonant interaction between a number of triple harmonics of the space charge wave occurred. Such three-wave resonances were also interconnected through certain common harmonics. It was shown that the conditions of plural three-wave parametric resonances between space charge wave harmonics, which are amplified due to two-stream instability, persisted in a two-stream electron beam despite the change in the velocity of the two-stream electron beam under the influence of the longitudinal electric field. It was found that the longitudinal accelerating electric field led to a significant increase in the frequency spectrum width of the multiharmonic space charge wave. The decelerating electric field reduced the width of the frequency spectrum of this wave, but the level of harmonic saturation increased. We proposed to use the accelerating electric field in the transit section of the multiharmonic two-stream superheterodyne free-electron laser to generate powerful multiharmonic electromagnetic signals with a wide frequency spectrum, including ultrashort clusters.

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