ABSTRACT
As we already mentioned in Chapter 1, at the time of the unforgettable Star Wars program, it became clear that, besides the usual H-Ubitrons, a whole series of other types of the FELs might be constructed. The plasma-beam superheterodyne FEL (PBSFEL) and the parametrical electron-wave superheterodyne FEL (PEWSFEL) have a special place in this series.
