Studies on the Phase Characteristic of S-band RKA: Reducing RF Phase Jitter by Reducing Intense Pulse Fluctuation

The phase characteristic is an important parameter of the intense relativistic klystron amplifier (RKA). But the intense pulse voltage produced by high-power pulse power source exists inherent fluctuations, which will affect the RF phase stability of RKA’s output microwave. In this paper, the one-dimensional nonlinearity theory is used to analysis the influences of electron beam voltage jitter on S-band RKA’s phase characteristic under different cavity parameters. Then the PIC simulations are performed to verify the theoretical results. By optimizing the structure parameters of cavities, the RF phase jitter caused by pulse voltage fluctuations is reduced effectively with experimental confirmation. The results suggest that the RF phase jitter caused by voltage fluctuations can be reduced effectively by optimizing the cavity parameters, especially the frequency of mid-cavity and output-cavity, and the Q value of output-cavity. By comprehensive optimizing cavity parameters, the phase jitter can be reduced by 30% while keeping the output power reduced within 15%. The results provide important guidance for improving the RKA phase stability.