Radiation damping in pulsed Gaussian beams

We consider the effects of radiation damping on the electron dynamics in a Gaussian-beam model of a laser field. For high intensities, i.e., with dimensionless intensity a₀1, it is found that the dynamics divides into three regimes. For low-energy electrons (low initial γ factor, γ₀) the radiation damping effects are negligible. At higher energies, but still at 2γ₀<a₀, the damping alters the final displacement and the net energy change of the electron. For 2γ₀>a₀ one is in a regime of radiation-reaction-induced electron capture. This capture is found to be stable with respect to the spatial properties of the electron beam and results in a significant energy loss of the electrons. In this regime the plane-wave model of the laser field provides a good description of the dynamics, whereas for lower energies the Gaussian-beam and plane-wave models differ significantly. Finally the dynamics is considered for the case of an x-ray free-electron laser field. It is found that the significantly lower intensities of such fields inhibit the damping effects.