Growth and saturation of stimulated beam modulation in a two-stream relativistic klystron amplifier

A two-stream relativistic klystron amplifier (RKA) is proposed in which the amplification of stimulated beam modulation is achieved via the unstable two-stream interaction rather than the use of passive cavities. After a calculation of the limiting current, the amplification and saturation of the stimulated beam modulation are analyzed using a cold-fluid model and particle-in-cell simulation. Good agreement is found between theory and simulation in the linear regime. Fully modulated intense relativistic electron beams are obtained at saturation. In the proposed scheme, substantial beam energy difference is required to achieve large instability growth.