Longitudinal Magnetic Field Effect on Wave Dynamics in Multiharmonic Superheterodyne FEL of Dopplertron Type with Helical Electron Beam

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

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

Е-mail lysenko_@ukr.net
Issue Volume 11, Year 2019, Number 6
Dates Received 25 September 2019; revised manuscript received 02 December 2019; published online 13 December 2019
Citation A.V. Lysenko, G.A. Oleksiienko, I.I. Volk, M.A. Korovai, J. Nano- Electron. Phys. 11 No 6, 06030 (2019)
DOI https://doi.org/10.21272/jnep.11(6).06030
PACS Number(s) 41.60.Cr, 52.59.Ye
Keywords Superheterodyne free-electron laser, Plasma-beam instability, Parametric resonance, Helical relativistic electron beam, Focusing magnetic field.

We performed the analysis of the longitudinal magnetic field influence on the amplification characteristics of the plasma-beam superheterodyne free-electron laser of dopplertron type with a helical relativistic electron beam in the framework of cubic nonlinear approximation. A right-polarized slow electromagnetic wave propagating towards the electron beam in the magnetized plasma-beam environment was used as pumping in the system under investigation. Based on the method of averaged characteristics, we acquired the system of differential equations describing the dynamics of harmonics of wave amplitudes. The saturation levels of electromagnetic waves were established. We took account of plural three-wave parametric resonant interactions of the space charge wave. We found out that such plural resonant interactions have a significant influence on the amplification properties of the investigated plasma-beam superheterodyne free-electron laser. In particular, they lead to the reduction of the saturation levels two times and more. We demonstrated that reduction of the longitudinal focusing magnetic field strength down to a certain critical value leads to the significant increase of the amplification rates along with the saturation levels of the electromagnetic signal wave (ten times and more). We have defined the minimal value of the magnetic field strength (critical value of the magnetic field strength) for the amplification regime in which the right-polarized electromagnetic wave is used as pumping. It is found that the investigated effect is related to the dependence of the conditions of the three-wave parametric resonance of the signal, pumping and the space charge wave on the longitudinal magnetic field strength. The growth rate related to the abovementioned three-wave resonant interaction depends substantially on the focusing magnetic field strength. We have demonstrated that plasma-beam superheterodyne free-electron laser of dopplertron type with a helical relativistic electron beam is able to form powerful coherent electromagnetic radiation in the millimeter wavelength band.

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