When taking into account the equilibrium self-fields of the beam, it has been confirmed that the motion of an electron in a helical wiggler with guide field may be chaotic. There is evidence of chaos from numerical calculations of non-zero Lyapunov exponents and Poincare maps.

The motion of an electron in a linearly polarized wiggler with an axial guide field is found to be nonintegrable. There is evidence for chaos from numerical calculations of Poincaré maps and of nonzero Lyapunov exponents. Resonances can be predicted from a one-dimensional Hamiltonian perturbed by a small ‘‘time-dependent’’ quantity.