Study On The Structure And Fabrication Technology Of Carbon Fiber Cathode With High Current Pulsed Electron Beam

High current pulsed electron beam(HCPEB)surface treatment technology began to burgeon in recent decades.Under the irradiation of HCPEB,thermal shock occurs on the surface of the material within several microns,induce the appearance of non-equilibrium micro structure,as a result,change the hardness,wear resistance,corrosion resistance and other properties of the material surface.Cathode is the production and emission location of electron beam.When the equipment is working,the pulsed negative high voltage is applied to the cathode,evoke the electron beam generation on the surface of the cathode through explosive electron emission,surface flashover,secondary electron emission and hot electron emission,then the electron beam is accelerated by the pulsed negative high voltage and transmission through the plasma channel which connecting the cathode and the working target to complete the modification of the material surface.Therefore,the study of cathode is of great significance to improve the working stability and surface modification effect of HCPEB.As a fiber material with good electrical conductivity,carbon fiber has strong thermal stability and comprehensive discharge mechanism,so it is a kind of electron beam emission material with broad application prospect.In this paper,through analysis the shortcomings of the existing carbon fiber cathode,based on the structure and operating vacuum parameters of HOPE-I high-current pulsed electron beam equipment,disigned and optimized a block composite cathode with carbon fiber lap structure.Through experiments,theoretical analysis,image analysis,structure simulation,numerical calculation and other means,the cathode fabrication process,technological parameters,comprehensive properties were studied.The fabrication process of the block composite carbon fiber cathode is as follows:Use2mm without glue carbon fiber and the resin alcohol mixture solution obtained by mixing the thermosetting liquid phenolic resin(viscosity 16000m Pa·s)and the anhydrous ethanol as the raw material for the experiment.Firstly,the carbon fiber was dispersed in the dispersant solution by mechanically stirred,then the phenolic resin ethanol mixture solution was added into the solution,and the mixture was evenly mixed under the water bath heating.Then the composite block of carbon fiber and phenolic resin carcking carbon was prepared by cold extrusion and hot sintering of the mixed composite slurry.Then the composite block is machined to obtain the required structure and dimensions.Finally,the finished cathode is obtained by repeated ultrasonic cleaning.In this paper,conductivity,vacuum compatibility,uniformity of density distribution,microsturcture uniformity of carbon fiber and process repeatability of cathode with different carbon fiber content were studied.It was shown that the cathode prepared by using 10g-14g carbon fiber(the density was about 0.16g/cm~3-0.21g/cm~3)has good performance.14g carbon fiber(density about 0.21g/cm~3)addition is the best choice for cathode prepared,because it is not only has good electrical conductivity,vacuum compatibility,fiber distribution uniformity,but higher process repeatability.The shape and size of the beam spot obtained by the discharge test of the cathode prepared by 14g carbon fiber are in good agreement with the cathode emission surface,and the uniformity of the beam spot is good.