Theoretical And Experimental Study Of Field Emission Electron Optics

In order to develop microwave and millimeter wave electric vacuum radiationsource devices with cold cathodes, the electron-optical system using carbon nanotubefield emission cathodes (CNFEC) is investigated in this paper. The main body ofresearch as follows;1．Based on the experimental results, the field emission simulation model ofCNFEC has been established by PIC simulation software of Magic. Pulsed andstraightflow field emission characteristics of CNFEC have been experimentallyinvestigated. The maximum emission current density of127mA/cm~2has been tested forCNFEC with a diameter of4mm round emission plane and the emission currentis16mA.2．The electron-optical system using a large area CNFEC is investigated, whichcan generate an electron beam with large current and high current density. Throughadding the mesh grid on the cathode surface, problems of the electron bunching andhigh electric field applied to the CNFEC surface have been solved and theelectron-optical system has been simulated by PIC simulation software. The effect ofthe mesh grid on the electron beam has been analyzed. And the influence of the anodevoltage and the axial magnetic field for the electron beam radius has been researched.The simulation results of the electron-optical system show that when the area of cathodeis3.03cm~2, a210mA/60kV electron beam can be produced, the current density is6.7A/cm~2and the maximum radius of the electron beam is1mm.3．A electron-optical system has been researched, which has been using a planarCNFEC without carbon nanotubes on the edge. The influence of focus electrode voltageand the Z coordinate of cathode for the electron beam radius has been researched. Thesimulation results of the electron gun show that when the emission area is50mm~2, a300mA/45kV electron beam can be produced, the minimum beam current density is38A/cm~2, the maximum radius of the electron beam is0.5mm and the average axialvelocity spread is0.2%.4．Beam-wave interaction in an8mm carcinotron oscillator has been investigated by PIC simulation software. The electron beam has been generated by orbicular CNFECelectron gun, and the slow wave structure is diaphragmatic waveguide. The simulationresults show that an output power of6.6%and0.83kW has been observed at34GHz.