Mode control in relativistic magnetrons and noise mechanisms in kW magnetrons

Summary form only given, as follows. Summary form only given. Experiments have been performed on both relativistic and nonrelativistic magnetrons. Relativistic (Titan) magnetron experiments (300-400 kV, 1-10 kA, 0.5 microsecond) investigate mode control with various output coupling geometries. Mode competition between the pi mode and the 2/3 pi mode has been characterized for two-versus-three output extractors for comparison with particle in cell simulations. Phase measurements and time-frequency-analysis are performed for mode identification. The peak microwave output power on the order 0.5 GW has been measured. Nonrelativistic (4 kV, <1A, kW microwave power) magnetron experiments are performed on commercial oven magnetrons for an in-depth investigation of crossed-field noise. Noise generation mechanisms are characterized, particularly as a function of cathode conditions. Several of Bill Brown's classic experiments on oven magnetrons have been repeated and extended For example, we investigated the transition to the quiet state by gradually turning off the cathode heater after oscillation has commenced.