Abstract: In the electron beam and ion beam device, the emission system affects the quality of the whole device. Therefore it is very important to analyse the emission system in electron beam device. This paper studies the method of numerical simulation of the electron emission. The planar diode model which is often used to calculate the emission of cathode is discussed and the error caused in the numerical simulation is analysed. On the basis of these discussions, this paper uses another method to simulate the thermal emission of cathode more precisely.

Key words: emission system, numerical simulation, planar diode, emission of electron