NUMERICAL COMPUTATION OF THE EMISSION CURRENT IN AN ELECTRON GUN

A computer program for calculating emission current in an electron gun has been worked out, and good agreement between calculations and experiments has been achieved. The computation model is based on the statistical theory of thermal electron emission, and the potential distribution in front of the cathode is equivalent to that o f an infinite planar diode in which the effect of the longitudinal thermal velocity of electron (ELTVE) is included.It is shown by the computation:1. In the case of CRT, the ELTVE must be taken into account. The calculated currents are greater than that estimated by the 3/2 power law and are closer experimental results than in the latter case. 2. In high density gun, the ELTVE is noticeable when it works at low voltage, but on the whole it is much smaller than in a CRT gun. 3. The ELTVE becomes significant as the difference between the operating current density and the cathode loading limit increases, and the effect remains unchanged when thedifference is beyond a certain value.