The Design And Characteristics Of Plasma Traveling Wave Tube Electron Optical System

Plasma technique was introduced in the research of high power microwave(HPM) sources in recent decade.The performance of HPM sources is improved much by filling plasma which is promising in this field.Filled-plasma travelling-wave tubes (FPTWT) is a part of them.It is the main task of this paper to research and design FPTWT's electron optics system and simulate it.Main works are as follows:1. To design electron guns with plane cathode according to high current electron optics theory. To select a cylindrical plane cathode; To design proper focus electrodes in order to control the formation of beam in methods of solving equations,electrobath and simulation aided by computer.To correct effects of anode hole and work out curves of designing guns;To discuss plasma cathode guns at last.2. To design an axial magnetic field.The cathode lies in 0.4-0.7 of peak value of the magnetic field and excursion channel in a uniform magnetic field to suppress space charge effects;To design transition section between the gun and excursion channel in converse computation.3. To design multistage depressed collectors.To classify electrons by their speeds, electrons with high energy are collected by low potential and those with low energy collected by high potential;To try to avoid second electrons' emission. Besides those air pump system was introduced briefly.4. To make PIC(particl-in-cell)simulations.To set up models of guns and magnetic field and simulate them in the vacuum and plasma,respectively.We found that plasma held back part of space charge effects and improved trajectory of electrons.But beam would oscillate and became instable as accretion of plasma density.By simulating again and again,we draw a conclusion Magic couldn't work when plasma density was more by far than beam electron density.At last a four-stage depressed collector was simulated.