Research On The Beam Control Technology Of Field Emission Electron Gun

Due to the fast response and miniaturization of field emission vacuum electronic devices(VEDs),its application advantages in VEDs have gradually become prominent.Carbon nanotubes(CNTs)are regarded as ideal field emission cathode materials because of their excellent electrical conductivity and good physicochemical stability.The CNTs cathode electron gun not only has good emission performance,but also has excellent potential in electron beam regulation.In recent years,CNTs cathode electron guns used in VEDs have become a new research hotspot,but there is no research result with high application value.In order to meet the demands of VEDs,not only the preparation of high-performance CNTs cathodes,but also the electron beams emitted by the CNTs cathode electron guns have a high compression ratio and good laminar flow.In response to the above requirements,this thesis has obtained the preparation process parameters of high-performance CNTs cathodes based on the previous research results of the research group.Through the electronic optical structure design and experimental verification of the CNTs cathode electron gun,a new type of CNTs cathode is obtained.A CNTs cathode electron gun with practical application value in VEDs.Specific research contents are as follows:(1)The preparation mold of the CNTs cathode was optimized to make the surface of the cathode more flat,and the preparation progress more convenient.In addition,the annealing temperature and duration parameters of the process for preparing CNTs cathodes by screen-printing were optimized,and the cathode emission performance was verified through a two-pole test.Finally,the best annealing parameters were obtained with an annealing temperature of 400?and an annealing duration of 3 hours.A negative high-voltage pulse power supply was used to conduct a two-pole test on a CNTs cathode sample with a diameter of 0.6 mm.Under the working voltage of3500 V(electric field intensity 8.75 V/?m),the emission current density is up to 12.2 A/cm~2,and the corresponding current is 34.6 m A.(2)The electron optical structure model of the laminar flow electron gun with a high compression ratio carbon nanotube cathode was constructed by CST software.The carbon nanotube cathode and cambered spokes were prepared by scanning the key parameters of the electron gun structure and combining the actual screen-printing method.Factors such as the feasibility of processing determine the best parameters of the electron gun.A simulation model of the arc-shaped toroidal cathode grid-controlled electron gun was established according to the best parameters,and a variety of comparative simulations confirmed the best performance of the electron optical structure.Under the working voltage of 15 k V,the working current of the electron gun reaches32.74m A,the grid interception rate is 27.7%,the range is 8.23mm,and the area compression ratio reaches 16.96 without the need of focusing pole.The simulation results show that the laminar flow of the electron gun is good.Finally,the electron gun was brought into the flow tube model for flow simulation experiments,and a periodic permanent magnet focusing structure was introduced to improve its flow rate.A 100%simulated flow rate was achieved at a magnetic flux density of 0.4T,and a periodic permanent magnet focus was obtained.The optimal magnetic flux density parameter of the system is 0.5T.(3)Based on the electron gun model established in the CST software,the arc-shaped toroidal cathode electron gun is processed and assembled.A negative voltage pulse power supply was used to carry out experimental studies on emission performance,current stability,grid interception rate,and flow rate of the arc-shaped toroidal cathode electron gun.It is measured that the electron gun's cathode emission current reaches 12.54 m A at a working voltage of 12 k V(electric field strength 8V/?m),and the grid interception rate is 38.9%.In the flow tube(?1.6 mm)test,the collector current reaches 5.48 m A,get a flow rate of 71.54%.When the working voltage is 9 k V(the electric field strength is 6 V/?m),the emission current of the electron gun is 5.20 m A,which drops to 4.98m A within 90 minutes,and the drop amplitude is 4.23%.The emission current of the electron gun is relatively stable.The research results of this thesis show that the carbon nanotube cathode electron gun has a good application prospect in microwave VEDs,and there is still a broad room for improvement.