The plasma klystron concept for high-power microwave amplifiers

Summary form only given. In order to eliminate some of these intrinsic problems in the high-power RKA (relativistic klystron amplifier), the author presents a novel plasma klystron amplifier, which consists of a relativistic annular electron beam propagating through a space between a plasma column and the drift tube wall. The annular electron beam premodulated at the first cavity in the klystron enters the space. An axial electric field accompanied by the modulated beam excites space charge waves in the plasma column, which acts like an inductive medium amplifying the electrostatic waves. The physical mechanism of self-amplification of the electrostatic waves is the two-stream instability. A theoretical model for describing the current modulation of the annular electron beam propagating through the space has been developed. The electron beam current is modulated by the amplifying electric field fed by the plasma column. The saturation distance of the current modulation is a weakly dependent function of the initial energy modulation at the first cavity. Thus, a relatively low-power microwave input may well excite the two-stream instability and deliver a highly modulated beam to the extraction cavity.