Demonstration of a Ka-Band Oversized Coaxial Multi-Beam Relativistic Klystron Amplifier for High Power Millimeter-Wave Radiation

We proposed an oversized coaxial multi-beam relativistic klystron amplifier (OCMB-RKA) with a new input coupler of lesser complexity giving enhanced input microwave power absorption rate for generating high power millimeter-wave radiation in Ka-band. The high-frequency structure of the OCMB-RKA was designed, fabricated, and cold-tested for results that agreed well with the simulated results. Furthermore, using the 3D particle-in-cell (PIC) code, the beam-wave interaction of the OCMB-RKA was simulated, considering two different materials (stainless steel and copper) making the interaction structure. When a 500 kV, 3 kA electron beam, and a focusing magnetic flux intensity of 1 T were adopted in the PIC simulation, a five-cavity OCMB-RKA yielded the output power of 610 MW at 30.525 GHz with the electronic efficiency of 40.7% and the saturated gain of 55.3 dB. Experimentally, the OCMB-RKA demonstrated its capability of generating high power Ka-band radiation typically of 390 MW power with the pulse width of 27 ns.