Forword Design Of Periodic Permanent Magnet Focusing System For Helix TWT

As an important part of the traveling wave tube,the periodic permanent magnet focusing system plays a key role in the performance of the traveling tube.The good electronic injection rate is the basic guarantee of traveling wave tube performance.The design of the permanent magnet focusing system can directly affect the whole performance.In the whole traveling wave tube design,the required magnetic field distribution is designed according to the parameters of the electron gun,interaction and other parameters,and then the magnetic system is designed according to the magnetic field distribution.However,after all,the designed magnetic field distribution is ideal,and it is inevitably different from the magnetic field distribution of the actual magnetic system.Therefore,it is necessary to study how to design a magnetic system based on the magnetic field distribution more accurately.In this paper,the design theory of magnetic system is combined with simulation calculation to study the design method of spiral periodic permanent magnet focusing system.This paper refers to the magnetic permeability method commonly used in designing periodic permanent magnet focusing system,which needs to use Besser in the magnetic permeability method.A complex function such as a function to solve the magnetic conductance in the magnetic system and then solve the outer diameter of the magnetic ring is replaced by a simulation method to solve the outer diameter of the magnetic ring.This paper simulates and analyzes the influence of various structural parameters of the magnetic system on the magnetic field distribution of the magnetic system.Simulation analysis of the ratio of the inner and outer diameter of the magnetic ring,the outer diameter of the magnetic ring and the height of the magnetic ring,the outer diameter of the pole piece and the outer diameter of the magnetic ring,the relationship between the height of the pole piece and the period of the magnetic field,the analysis shows that the peak value of the magnetic field varies with the height and outer diameter of the magnetic ring.The increase first increases and then decreases.As the ratio of the inner and outer diameters of the magnetic ring increases,the trend begins to decrease.The peak value of the magnetic field decreases with the increase of the outer diameter of the pole piece and the outer diameter of the magnetic ring,and the relationship between the peak value of the magnetic field and the height of the pole piece and the period of the magnetic field also shows a relationship of increasing first and then decreasing.This paper simulates the magnetic ring asymmetry structure and analyzes the magnetic field symmetry of the asymmetric magnetic system.The axisymmetric magnetic system,the asymmetric magnetic system,the magnetic field distribution of the magnetic system of the pole piece structure are analyzed separately,and the magnetic field distribution of the three different structural magnetic systems is analyzed to constrain the electron injection,and the radius of the electron injection channel The symmetry of the magnetic field is compared with the symmetry of the magnetic field,and the pole shoe can effectively reduce the asymmetry of the magnetic field.The research results show that the pole piece can effectively reduce the magnetic field asymmetry of the asymmetric magnetic system,which points out a new method for suppressing the magnetic ring assembly error that the magnetic system may produce during the assembly process.The high-band magnetic system has a small structure,and it is more prone to errors in the assembly process,causing the electronic injection to hit the spiral line,and the electron injection flow rate is lowered.This method of reducing the asymmetry of the magnetic field will play an important role in the high band.