Chaotic electron dynamics for relativistic-electron-beam propagation through a planar wiggler magnetic field.

It is shown that the motion of an individual test electron in a low-density relativistic electron beam propagating through a realizable planar-wiggler magnetic field is nonintegrable and can become chaotic. The chaoticity, which is induced by the transverse spatial inhomogeneities in the wiggler field, poses limits on the wiggler field amplitude and the beam size for beam propagation and free electron laser operation. An approximate condition that determines the onset of chaoticity-induced beam degradation is derived analytically and found to be in good qualitative agreement with the numerical simulations using the Poincar6 map. PACS numbers: 42.55.T, 41.70.+t, 05.45