Three-dimensional Particle-in-cell Simulation Study of a Frequency Tunable Relativistic Magnetron

A three-dimensional particle-in-cell (PIC) code, MAGIC3D, is used to simulate an A6 relativistic magnetron with metal tuner. As inserting six conducting rods into the resonators in regions where the RF magnetic field is high, the resonant frequency of 2pi-mode (n=6) of the A6 magnetron is tuned over the range from 4.27 to 4.47 GHz. The simulations show that with perturbed RF magnetic fields caused by metal tuner, the performance of the A6 magnetron in terms of radiation output power, frequency spectrum, and efficiency is superior compared with those using the uniform RF magnetic fields. Maximum output power of A6 with three tuners is 600 MW at 4.4 GHz, corresponding to a magnetron efficiency of 7.2%, which is about 20% higher than the conventional A6 magnetron where the axial external magnetic field is 5.5 kG and the beam voltage and the total current are 360 kV and 23 kA, respectively. When the tuner position of three metal rods is 8 cm, which is adjusted to get maximum power, a spectral amplitude in the pi-mode is lower 33 dB in power than the 2pi-mode.