| The traveling wave tube is a type of vacuum electronic device that has a wide frequency band,a high single tube gain,good nonlinear performance,high power,and low noise performance,and is used in a variety of communications,radar,and military countermeasure systems.The electron-optics system is required to provide high quality,small lateral size,and high current electron beam when the traveling wave tube develops to high power,high frequency,and downsizing.Sheet beams have been extensively investigated and deployed due to their ability to enlarge the broadside size and carry higher currents while keeping lower current densities.For focusing electron beams,the magnetic focusing system is a crucial structure.Nonlinear pole-shoe materials are frequently used in the simulation design of magnetic systems,which increases simulation computation and increases the time spent on magnetic system simulation,producing significant problems in the design of electron-optics system.The magnetic field can be calculated quickly using two-dimensional modeling in electromagnetic simulation software such as Maxwell for the traditional focusing system of circular electron beam;however,the focusing system of ribbon beam,for example,the commonly used PCM,rectangular magnetic block,and rectangular channel,does not have axisymmetry,and the traditional two-dimensional modeling method is not applicable.PCM's quick calculation is hindered by a lack of efficient methods.As a result,developing a theory of magnetic systems with non-axisymmetric structures and a quick design procedure for magnetic fields is critical for reducing the design cycle and increasing the design efficiency of ribbon beam electro-optics systems.This research develops a detailed theoretical examination of PCM with offset poles based on this.The magnetic field calculation is examined using the current source equivalent model and the flux path model.Fast computation and inverse design of magnetic fields are achieved via programming by merging these two separate model calculation approaches via parameter equivalence.The electromagnetic simulation software CST also verifies and analyzes it.The theoretical study of flux routes,as well as the computation and verification of magnetic fields,are then carried out for PCMs with various structures.Theoretically calculate and construct the attainable theoretical three-dimensional magnetic field using the PCM simulation model,and replace the actual magnetic field with ribbon electron beam for joint simulation to realize the fast calculation and optimization of PCM.Finally,the simulation design of a W-band high-power sheet beam electron-optics system is carried out in accordance with the design requirements of the sheet beam traveling wave tube,and the PCM magnetic system with offset poles is used to focus the electron beam,and the electron circulation rate reaches 100%.The importance and principle of offset poles are also discussed. |
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