Research On The LaB₆ Field Emission Electron Gun

As the core component of micro-detection equipment such as the electron microscopes and X-ray tubes,the electron gun plays an important role in industrial inspection,medical imaging and other fields.Compared with traditional heat emitting cathodes,the field emission cathode has the advantages of being able to operate at low temperature,high current density and good switching performance.Therefore,using a field emission cathode as an electron source device,designing and developing a field emission electron gun with small volume,low power consumption,high current density,and small focus is of great significance for improving the performance of mobile portable micro-detection equipment.In this paper,using OPERA-3D simulation software,a field emission gun with a single-crystal LaB₆ field emission cathode as an electron source was designed and manufactured for mobile portable micro-detection equipment.After completion of the preparation,the field emission performance of single crystal LaB₆ field emission cathode and field emission electron gun was also tested.The main contents and conclusions are as follows:1.The LaB₆ field emission electron gun designed in this paper contains four main electrode structures:cathode,grid,focusing pole and anode.Among them,the grid electrode,the focusing electrode and the anode together constitute a film hole electrostatic lens.By changing the potential of the focusing electrode,the anode beam spot diameter of the LaB₆ field emission electron gun can be effectively adjusted.Using OPERA-3D software to simulate the LaB₆ field emission electron gun,a set of electron gun electrode structure parameters satisfying the design requirements of this article was finally obtained.When the diameter of the gate hole is 4mm,the upper diameter is 6mm,the voltage is 1350V;The diameter of the focusing hole is 7mm,the upper diameter is5mm,the voltage is 0V;The anode is 4mm from the upper surface of the focusing electrode,and the voltage is 30000V,the anode current of the LaB₆ field emission electron gun is 14.1?A,and the diameter of the anode electron beam spot is 0.3mm.2.The single crystal LaB₆ field emission cathode was prepared by WEDM assisted the electrochemical etching,and the field emission performance of the cathode after the preparation was tested.The result shows,when the etching solution is a mixture of concentrated hydrochloric acid,absolute ethanol and water with a volume ratio of1:30:30,the corrosion current is 100 mA,and the etching time is 40 minutes,a single-crystal LaB₆ field emission cathode with good surface morphology can be obtained.After field emission performance test,the turn-on voltage of the single crystal LaB₆ field emission cathode was 850V,which was in accordance with practical application requirements.When the anode voltage is 1350V and the cathode-anode distance is 0.18mm,the current is 45.5?A,and the F-N curve is satisfied.3.According to the simulation results of OPERA-3D software,the electrodes and parts of the LaB₆ field emission electron gun were designed,processed,assembled and tested.Finally,after field emission performance test of the electron gun,a LaB₆ field emission electron gun with an anode emission current of 13.2?A and an anode beam spot diameter of 0.4mm was obtained.