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Irregular phase-space orbits of the electrons are harmful to the electron-beam transport quality and hence deteriorate the performance of a free-electron laser(FEL).In previous literature,it was demonstrated that the irregularity of the electron phase-space orbits could be caused in several ways,such as varying the wiggler amplitude and inducing sidebands.Based on a Hamiltonian model with a set of self-consistent differential equations,it is shown in this paper that the electronbeam normalized plasma frequency functions not only couple the electron motion with the FEL wave,which results in the evolution of the FEL wave field and a possible power saturation at a large beam current,but also cause the irregularity of the electron phase-space orbits when the normalized plasma frequency has a sufficiently large value,even if the initial energy of the electron is equal to the synchronous energy or the FEL wave does not reach power saturation.
Irregular phase-space orbits of the electrons are harmful to the electron-beam transport quality and hence deteriorate the performance of a free-electron laser (FEL). Previous previous literature, it was demonstrated that the irregularity of the electron phase-space orbits could be caused in several ways, such as varying the wiggler amplitude and inducing sidebands.Based on a Hamiltonian model with a set of self-consistent differential equations, it is shown in this paper that the electron beam normalized plasma frequency functions not only couple the electron motion with the FEL wave, which results in the evolution of the FEL wave field and a possible power saturation at a large beam current, but also cause the irregularity of the electron phase-space orbits when the normalized plasma frequency has a substantial large value, even if the initial energy of the electron is equal to the synchronous energy or the FEL wave does not reach power saturation.