FREE-ELECTRON LASERS WITH STATIC AND DYNAMIC PLASMA WIGGLERS

In free electron lasers, plasma wigglers of static and dynamic types m ay be used. In the case of a static plasma wiggler a spatially modulat ed plasma density results in a periodic dielectric permittivity, but p umping electromagnetic fields are absent. A dynamic plasma wiggler ari ses when an electromagnetic wave propagating in a plasma is scattered by an electron beam. The wave fields act on beam electrons but modulat e plasma particles also. Two mechanisms are responsible for the intera ction between an electron beam and electromagnetic waves. One of them is analogous to that in usual FELs and exists only in dynamic plasma w igglers. Another mechanism is conditioned by space-temporal modulation of the density and velocity of plasma particles and exist in both sta tic and dynamic plasma wigglers. The contributions of the two mechanis ms into the interaction process may be comparable. Both types of magne tized plasma wigglers are considered in a linear approximation.