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Chakhmachi, A.

Paper Title Page
MOPPH012 Conservation Laws in Quasilinear Theory of Raman Free-Electron Laser 46
 
  • A. Chakhmachi
    AEOI, Tehran
  • B. Maraghechi
    AUT, Tehran
 
  A quasilinear theory of the free-electron laser, in Raman regime, is presented to establish that conservation laws on number, energy, and momentum are upheld. A high density electron beam is assumed so that the space-charge potential is no longer negligible. A sufficiently broad band spectrum of waves is assumed so that saturation will be due to the quasilinear spread of the beam electrons. Otherwise, for the single mode excitation, saturation will be due to the electron trapping in the space-charge potential. It is shown that the quasilinear slow variation of the background distribution function is in the form of the diffusion equation in momentum space. An expression for the time evolution of the spectral energy density is derived. Conservation laws to the quasilinear order (second order) are derived and are proved to be satisfied. Results of the present investigation may be used to study the quasilinear saturation of free-electron laser in the presence of the space-charge wave.