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Free-Electron Laser Amplifier Driven by an Induction Linac

  • V. Kelvin Neil
Part of the NATO ASI Series book series (NSSB, volume 178)

Abstract

A free-electron laser (FEL) directly converts the kinetic energy of a high-brightness, relativistic electron beam into coherent radiation. It is a classical device, much like a traveling wave tube. In an FEL amplifier the conversion takes place in a single pass through a wiggler magnet, therefore, the fraction of kinetic energy converted must be high if the device is to be efficient. Since the conversion is a rapidly increasing function of the electron beam current, a current of 1 kA or greater is desired. The particle energy required depends on the wavelength of coherent radiation. For a given wiggler wavelength, λW, wiggler magnetic field B, and radiation wavelength, λS, there is a resonance condition that determines the proper electron energy. This condition will be derived later in this paper and is
$$ {\lambda_S} = \frac{{{\lambda_W}}}{{2{\gamma^2}}}\left[ {1 + \frac{1}{2}{{\left( {\frac{{eB{\lambda_W}}}{{2\pi m{c^2}}}} \right)}^2}} \right] $$
(1)
in which γ is the electron energy in units of the rest energy, mc2. If B and λW do not vary with position as the particle’s energy is converted and γ decreases, the condition is no longer satisfied at some position and saturation results. However, if B or λW or some combination varies with axial position, the resonance condition can be maintained. The conversion efficiency (also called extraction efficiency) is greatly enhanced and the output radiation energy increased.

Keywords

Lawrence Livermore National Laboratory Electron Beam Current Travel Wave Tube Small Signal Gain Betatron Oscillation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Press, New York 1988

Authors and Affiliations

  • V. Kelvin Neil
    • 1
  1. 1.Lawrence Livermore National LaboratoryLivermoreUSA

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