Design of a Free-Electron Laser Using an Electric Wiggler Supplemented with a Magnetic Wiggler Based on Quantum-Wiggler Electrodynamics

Abstract

In this letter, we assume that the electron beam is in the Compton region, i.e., neλ . 1 by definition, where ne and λ are the electron density and the laser wavelength, respectively. In order for an electron to emit photons in the axial direction, it should have a transverse momentum. Thus, in order to build a free-electron laser (FEL), a magnetic wiggler, which makes the electrons to have transverse momentum, is needed. However, in the FEL using a magnetic wiggler (‘MFEL’) [1], the attenuation due to scattering predominates the amplification due to net stimulated emission when the laser intensity is below a certain level determined by the number of incident laser photons in the interaction volume. The interaction volume is considered to be on the order of λ. Hence, we can assume that the number of the incident laser photons in the interaction volume at z is given by Np(z) = np(z)λ, where np = I(z)/c~Ω with I(z) and Ω being the intensity at z and the frequency of the incident radiation, respectively. The laser radiation incident on an electron is not scattered when Nc 1 [2]. If scattering predominates net stimulated emission and is constant, the profile of the number of incident photons in the interaction volume asymtotically approaches [cf. Eq. (4) of Ref. 3]