EXCITATION OF ELECTROMAGNETIC-RADIATION IN AN ANNULATE PLASMA WAVE-GUIDE

Linear and nonlinear theories of the instability of a monoenergetic el ectron beam in an annulate hybrid slowing-down waveguide with and with out an external magnetic field are developed. The beam instability is shown to be dissipative in nature, and the role of dissipation is play ed by the plasma wave energy expended on the excitation of electromagn etic radiation. Numerical analysis shows that the excited radiation ra ises the efficiency with which the beam loses its energy. It is import ant that an increase in the power of the excited microwave radiation i s not accompanied by an increase in the amplitude of the electric fiel ds in the plasma. Consequently, the power of generators with such hybr id waveguides can be increased in a certain range without causing the: onset of various parasitic plasma instabilities, the most dangerous o f which are low-frequency instabilities.