Practical design of the electron gun for a microfocus x-ray sourcea)

A practical electron gun including the cathode, the grid, the anode, the insulator, the joint flange, and the gun chamber was developed to build a 90 keV microfocus x-ray source with high performance. Based on the electron emission theory at metal surface, the cathode, the grid, and the anode were optimized to achieve fine crossover, high maximum brightness, and high effective brightness with 1 mA beam current. In order to improve stability of the gun, the grid, the anode, the insulator, the joint flange, and the gun chamber were designed and fabricated to eliminate discharge at the peak and the creepage along insulator. Results show that the effective brightness of this model is 1.05×105A/(cm2 sr) with 1 mA beam current, and the microfocus x-ray source has a resolution below 4 μm when the target current is 100 μA. The practical electron gun can improve the beam current quality of the microfocus x-ray source.