Abstract：There will be an electrostatic field between cathode grid and anode in directly heated electron guns. This
electrostatic field has a primary convergence effect on the beam current. The change of distance between anode and cathode,
and the change of grid and anode shape will affect this electrostatic field and ultimately affect beam quality. Aiming at
the problem that the electrostatic field and the movement track of electron are both difficult to measure directly by conventional
method, this paper built a 1 ∶ 1 3D model and simulated the whole process of beam generation by using the simulation
software CST particlestudio. By using the single variable method and analyzing the date, we obtain electrostatic field
distribution, clear electron movement track under different conditions and graph of each variable parameter and beam current
energy density at the focus position. Finally, the best structure size for beam quality is obtained. Then we took actual
welding test on aluminum alloy plate with optimized electron gun structure. The welding seams we got are better than the
original electron gun structure, which proves the simulation result is correct. This method provides a basis for the improvement
of the beam quality of the existing electron guns and future design of the electron guns.
2017, 
