Design And Development Of Electron Gun Based On Quasi-Macroscopic Carbon Fiber And Study On Electron Optical Properties

The miniaturization of components has become a widespread trend in various industrial domains,thereby imposing greater demands on the production of small parts.Traditional mechanical processing methodologies are limited by precision and tool effects,rendering them incapable of expanding towards micro-sized parts beyond the sub-micron to sub-millimeter scale.In turn,photolithography-based micro-fabrication technology lies at the mercy of material-based properties and three-dimensional structures of the parts,limiting its applicability to sub-micron scales and impeding progress into the realm of metal micro-parts.The deployment of additive manufacturing technologies using electron beam melting as a heating modality presents inherent advantages in the production of complex metallic components.However,such methods are constrained by the diameter of the electron gun beam,thus precluding the manufacture of smaller parts.The recent emergence of carbon materials for field emission device applications presents a possible solution to this issue,albeit requiring further research material morphology and corresponding supporting devices.To this end,this study employs quasi-macroscopic carbon fibers as filaments,field emission as the operative mode,and combines simulation and physical verification techniques to design the corresponding cold cathode electron gun structure and explore electron emission functionalities and electron optical properties,with ensuing device trial productions.The key aspects of this research undertaking involve:(1)Generating and preparing quasi-macroscopic carbon fiber(QMCF)filaments with axially symmetric structures through methane cracking catalyzed by iron particles.Exploration of the device formation process and electron emission functionalities was carried out.Characterization tests revealed the QMCF filaments’diameters mostly ranging between 10-20μm and lengths at the centimeter level,categorizing them as quasi-macroscopic.Furthermore,the unique hemispherical emission end provided a solid foundation for electron emission and beam convergence for field emission electron guns.Field emission functional assessment of this material showed that the total emission current can attain values surpassing 1mA.The electron beam spot test and finite element simulation jointly determined that the field strength of its emitting surface is indeed a stair-like distribution,and the effective emission angleθis concentrated within a range of 30°.(2)Simulation calculations on typical triode electron guns in tandem with subsequent experimental validation served to determine the influence of gate electrode structure parameters on electron gun emission performance.Subsequently,the optimal working parameters and structures were established,thereby enabling the design and customization of a triode electron gun’s structure accordingly.The physical object was tested according to simulation parameters post-equipment modification,part pre-processing,and assembly.Such tests revealed beam spot diameters around 0.5mm,with maximum emission current reaching 0.271mA,the corresponding current density is539.41A/cm~2.(3)Incorporating a focusing pole to upgrade the triode electron structure into a quadripole structure further enhanced the electron beam convergence effect.Simulation assessments spanning quadripole electron guns at 30kV and 60kV,while reducing overall size and boosting assembly accuracy,facilitated simulated design and manufacture of multi-pole electron guns operating at 60kV.Such improvements decreased the electron gun’s beam spot diameter to less than 20μm.Physical objects were subsequently designed and assembled to study the impact of QMCF morphology on electron gun effectiveness in a quadripole gun.Experimental validation at 30kV revealed results comparable to those obtained from simulations at 30kV.The aforementioned research results provide some reference value for constructing electron micro-beam additive manufacturing and electron gun and electron optical systems with greater academic expression.