RF Priming Experiments on a Relativistic Magnetron

Summary form only given. Research is underway to investigate radio frequency (RF) priming of relativistic magnetrons for rapid startup and reduced mode competition. Experiments utilize the MELBA-C to drive the Titan 6-vane relativistic magnetron at parameters: V=-300 kV, I=1-10 kA, e-beam pulselength=0.5 musec, microwave power=100-500 MW, microwave frequency=1-1.3 GHz (with tuning). MELBA-C´s ceramic insulator enables base vacuum down to 8.5E-8 torr. The RF priming source is a 230 kW, 3 musec, pulsed magnetron from AFRL operating at 1.27-1.32 GHz. Tuning stubs are utilized in the Titan tube to adjust the frequency of the relativistic magnetron to match that of the priming magnetron. Microwaves are injected into 1 of the 3 open coupling slots in the MELBA-C relativistic magnetron. Time frequency analysis (TFA) of the magnetron´s microwave output shows a clear effect of the RF priming on the relativistic magnetron. Frequency locking is observed when the priming RF frequency is sufficiently well matched to that of the relativistic magnetron. When the priming RF frequency is detuned, mode-beating is observed in agreement with the theory. Concurrent with the experiments are simulations utilizing the MAGIC 3D code to investigate the effects of RF priming on the relativistic magnetron.