Numerical Simulation About Beam Wave Interaction Of Klystron

As a microwave tube with high power and high gain,the klystron is widely used in high-energy particle accelerators,communications,radar,electronic countermeasures and other fields.With the increasing demand of the performance requirements of klystrons in various fields,the research on klystron CAD software has become one of the hotspots in the research of klystrons.The beam wave interaction has a direct impact on the output power,bandwidth and other indicators of the klystron.Therefore,it is an urgent requirement for the design and development of klystron to establish a fast and accurate theoretical analysis model of beam wave interaction,carry out accurate and efficient numerical simulation of beam wave interaction,and then improve and optimize the performance of klystron.In view of the complex structure of the klystron,the accuracy,ease of operation,and solution speed of commercial CAD software need to be improved.The development of software dedicated to solving the beam wave interaction of the klystron can provide a good boost for the development of the klystron.Based on the above reasons and a large number of references,this paper studies the theoretical model of klystron beam wave interaction.The main work points and innovations are as follows:1.Based on the time-domain TESLA beam wave interaction simulation method of the klystron and the one-dimensional electronic disc model,the one-dimensional steadystate frequency-domain beam wave interaction simulation method of the cylindrical electron beam klystron is studied.When carrying out resonant cavity beam wave interaction simulations,this paper first starts from Maxwell's equations,using the orthogonality and completeness of the eigenmodes,and uses the generalized telegraph equations and mode expansions of the field to quickly solve the high-frequency electromagnetic field in the cavity and electron beam channel of klystron.Then combined with the space charge field and the external focusing magnetic field,the electron beam is gradually advanced from the starting position of the resonant cavity,and then the current source distribution is updated according to the particle trajectory.The current source excites the electromagnetic field in reverse until the end position of the resonant cavity,that is,an iteration is completed,and the above process is repeated until the highfrequency electromagnetic field and particle motion trajectory reach a stable state;In the simulation of the beam wave interaction in the drift section,the space charge field and the external focus magnetic field are used to gradually propel the electron movement.2.Based on the one-dimensional steady-state frequency domain beam wave interaction simulation method,this paper uses the gap distribution function to express the gap electric field distribution,and also uses the numerical value of the generalized telegraph equation in the electron beam channel to solve the problem.In addition,MATLAB has also been used to develop and design a cylindrical electron beam klystron with a graphical interface beam wave interaction calculation software,and the X-band klystron has been simulated and solved.Comparing with the simulation result of AJDISK software,a relatively close result is obtained.3.In this paper,the one-dimensional steady-state frequency-domain beam wave interaction simulation method of the sheet electron beam klystron has been studied.First,a one-dimensional electronic rectangular sheet model is established,and then the orthogonality and completeness of the eigenmodes of the rectangular waveguide are used in combination with the resonance mode in the cavity to obtain the electromagnetic field in the electron beam channel and the high-frequency electromagnetic field in the resonant cavity.After that,the space charge force between the slices is calculated by the Green's function method,combined with the high-frequency electromagnetic field to advance the particle movement,and then the current source is solved by the obtained particle trajectory.The current source excites the high-frequency electromagnetic field,and repeats this until the steady-state resonant cavity converges voltage and current.From the interaction inlet to the interaction outlet,the beam wave interaction calculation in the resonant cavity and the drift section is performed alternately to complete simulation of steady-state beam wave interaction characteristics in the klystron.Then,MATLAB was used to develop and design the beam wave interaction calculation software of the sheet electron beam klystron with a graphical interface.Finally,a W-band klystron was simulated and solved and compared with the simulation results of CST particle studio,and analyzed the reasons for the difference between the software and CST particle studio results.The software for calculating beam wave interaction of cylindrical electron beam klystron and sheet electron beam klystron designed and developed in this paper has the advantages of high efficiency and stability of frequency domain method and simple operation,which greatly improves the simulation speed of beam wave interaction of klystron and can be used for numerical simulation of beam wave interaction in single gap klystron and Extended Interaction klystron.