Stability Analysis for Electron Orbits in a Harmonic Wiggler

초록

A high-power free-electron laser is operated at a high electron beam current and high wiggler magnetic field, and the stability of the electron motion under those conditions is important for obtaining sufficiently large gain and high efficiency. In this study, a harmonic wiggler was used to improve the stability of the electron beam. Guiding-center variables were applied to analyze the complex electron motion in the electric and magnetic fields in combination with the wiggler magnetic field, the axial-guide magnetic field, and the self-generated field. The steady-state orbits of an electron in the harmonic wiggler were calculated analytically, and the Poincare surface of section plot was generated to distinguish between regular and chaotic behavior in the electron orbits. Finally, when the harmonic wiggler was used, the electron orbits were found to become stable compared with those in the conventional wiggler.

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