Nonlinear short-pulse propagation in a free-electron laser.

With one-dimensional time-dependent Maxwell-Lorentz equations, we have numerically investigated the nonlinear short-pulse propagation in a free-electron laser (FEL). Considering the pulsed electron beam and the cavity deturning, we describe a spiking behavior and the dissipative dynamics in a FEL oscillator. We show that the spiking behavior is well understood by superradiant pulse propagation and its dynamical regimes are closely related to a bifurcation and the chaotic transition in the nonlinear dissipative dynamics. The scaled synchrotron slippage distance (L syn /L s ), where L s is the slippage length and L syn is the slippage distance in a synchrotron period, plays an important role in determining the dynamical regimes