The Study of Permanent Magnet Structure for Compact A6 Relativistic Magnetron with Radial RF Extraction

Typical S-band A6 magnetrons have radial extraction output which is perpendicular to the direction of magnetic field inside magnetron. For this structure, generally a pair of Helmholtz coils are set on both sides of RM to provide magnetic field in the interaction region. However, despite of advantages of coils like adjustable magnetic field, it usually make the whole magnetron system heavy and bulky. It's also due to additional equipment like power supply for the coils. Especially when strong magnetic field is required for relativistic scale, it becomes much burden to system compactness. In the meanwhile, if permanent magnet structure is adopted, it can make the relativistic magnetron system more simpler and lighter compared to the ones with coils. In this study, we designed and analyzed different structure of permanent magnets to avoid pre-described radial output structural disadvantage for providing uniform and strong enough magnetic field in the electron interaction region of AK gap in relativistic magnetron. In consequence, we could produce uniform magnetic field of over 0.4T which is comparable with Helmholtz coils by applying radially magnetized permanent magnets. Assembled with A6 relativistic magnetron, it was successfully observed for the compact system to generate S-band high power microwave in hundreds of maegwatt scale.