How Magnetic Field Inhomogeneity of Plane Wiggler Affects Spontaneous   Radiation of Electrons
  The spectral distribution of spontaneous emission of electrons moving in a plane wiggler with inhomogeneous magnetic field is calculated. We show that electrons do complicated motion consisting of slow(strophotron) and fast(undulator) parts. The equations of motion are averaged over fast undulator part and we obtain equations for connected motion. It is shown, that the account of inhomogenity of the magnetic field leads to appearance of additional peaks in the spectral distribution of spontaneous radiation. 
E.A. Ayryan, A.H. Gevorgyan, M. Hnatic, N.Sh. Izmailian, V.V. Papoyan,   K.B. Oganesyan
physics.acc-ph