Influence of the cathode position on beam current characteristics in the thermionic electron gun

Purpose The research focuses on the simulation of influence of cathode positions on beam current characteristics in the thermionic electron gun.
Methods The electric field distribution, bias voltage range and electron beam quality under different cathode positions were simulated by CST software.
Results Changes in the cathode position can cause changes in the electric field distributions under the cathode emission surface change, thereby changing the size of the effective emitting area and affecting the relationship between the bias voltage and beam current.
Conclusions Only when the cathode is installed in the proper positions, the beam current and the bias voltage have an approximately linear proportional relationship. When the cathode is installed improperly, the electron beam emission is disordered, resulting in decreased electron beam quality.