Progress on a one gigawatt, one microsecond pulse length, high current relativistic klystron

The development of a one gigawatt, high current relativistic klystron tube is underway for producing one microsecond long, 1.3 GHz microwave pulses at a 5 Hz pulse repetition frequency. This paper describes the theory, modeling, and experimental development of the microwave tube. The one microsecond pulse length is almost an order of magnitude beyond what has been achieved with a high current relativistic klystron. Achieving a peak power approaching 1 GW for 1 μs requires a stable electron beam on that time scale, and an optimized extraction efficiency in the output cavity. The microwave tube design was guided by theory and particle-in-cell code modeling that relate output cavity extraction efficiency to the amplitude of the beam harmonic current modulation and output cavity shunt impedance. Current experimental results are presented. The 1 MV, 10 kA, 1μs pulse length, 5 Hz pulse-repetition-rate pulsed power modulator used to power the relativistic klystron is also described. 4 figs., 6 refs