Performance enhancement of a strapped magnetron using a non-uniform magnetic field

This paper investigates the effect of different distributions of magnetic fields on the magnetron performance, using the 3D version of the MAGIC code. The computer model of a ten-vane strapped magnetron used in microwave oven was set up, incorporating all the structure details, such as the helical cathode, output coupling circuit and magnetic pole pieces. The simulation of the magnetron performance was carried out using three different distributions of magnetic fields, i.e. the uniform distributed one (axial component only), the step distributed one and the real distribution obtained from computer modelling with the verification in measurement. The simulations show that with the uniform magnetic field, the performance of the magnetron in terms of oscillation start up time, frequency spectrum and stability is inferior compared with those using the non-uniformed magnetic fields. In fact the non-uniform magnetic field can substantially reduce the start up time and improve the frequency spectrum and stability. This observation suggests that non-uniformed magnetic field is a better choice for the magnetron operation, which challenges the conventional approach in magnetron design, in which a uniform magnetic field is always perused. Further experimental studies will be carried out to verify this result.