Injection Locking Of A long-pulse relativistic magnetron

We report the injection locking results of a long-pulse (200-400 ns) high power (25 MW) relativistic magnetron. The cold-cathode magnetron structure is driven by a high power modulator to generate S-band output at 3.3 GHz. Reproducible final phase-locked angle is achieved with injection power ratio as low as 1:200. The locked states are phase stable to within ±5° during the pulse. Repetition-rated operation at 5 Hz produces average powers higher than single shot systems. Phase locking physics is studied by parametrically scanning the injection frequency and varying the injection power. Important effects due to frequency pushing are identified. The measured locking bandwidth agrees well with a theory which takes into account frequency pushing effects. The measured dependence of final locked phase on injection frequency and injection power also agrees well with theory.