ABSTRACT
Today's highest-power generators of electromagnetic waves involve the use of high-intensity relativistic electron beams. One of the principles of these generators makes use of the phenomenon of formation and subsequent high-frequency oscillations of the virtual cathode in the electron beam at the super-Bursian current. The corresponding devices are known as vircators (and sometimes as turbotrons). Another principle uses the effect of relativistic transformation of the frequency of an electromagnetic wave when it is scattered on the electron beam. Depending on the concentration and energy of beam electrons and on the oscillation wavelength, the scattering occurs either on individual particles or on electron waves. Both types of devices are usually referred to as free electron lasers (or masers). The amplification coefficient of a Raman maser can be considerably improved by preliminary modulation of the electron beam by an electromagnetic wave.
