New developments in the relativistic klystron amplifier technology

Development of relativistic klystron amplifiers (RKAs) at NRL has set world records in peak RF power generation. Using RKAs, microwave power has been generated in excess of 10 GW at a frequency of 1.3 GHz and with energy of 1 kJ per pulse. A new generation of RKAs is being developed overcoming current limitations and providing a technology which will be compact, cheap, and equally efficient from 5 to 10 GHz (>75%). This can be achieved by using a “triaxial” RKA geometry in which an annular electron beam is surrounded on the outside and on the inside by metallic structures. This geometry can handle a large diameter electron beam of high current and high power, which is constant throughout the frequency range. Inductively loaded wide gaps, stacked with thin metallic washers, will be used to modulate the electron beam and to extract RF with high efficiency (>75%), while avoiding breakdown and DC space charge limits.