Model for intensity calculation in electron guns

Abstract

International audienceThe calculation of the current in an electron gun structure is one of the main investigations involved in the electron gun physics understanding. In particular, various simulation codes exist but often present some important discrepancies with experiments. Moreover, those differences cannot be reduced because of the lack of physical information in these codes. We present a simple physical three-dimensional model, valid for all kinds of gun geometries. This model presents a better precision than all the other simulation codes and models encountered and allows the real understanding of the electron gun physics. It is based only on the calculation of the Laplace electric field at the cathode, the use of the classical Child-Langmuir's current density, and a geometrical correction to this law. Finally, the intensity versus voltage characteristic curve can be precisely described with only a few physical parameters. Indeed, we have showed that only the shape of the electric field at the cathode without beam, and a distance of an equivalent infinite planar diode gap, govern mainly the electron gun current generation

100 years of the physics of diodes

“…[7][8][9][10][11][12][13] Because of its simplicity and accuracy, this capacitance or transit time model is of great utility to study a short pulse diode, 12 and more recently the quantum regime. 89 In fact, though only with ad hoc justification, it has long been noticed by electron gun and (cathode ray tube) CRT designers that the SCL beam creation is ruled only by the vacuum electric field on the cathode (without beam) E c and is based on the very simple scaling law [90][91][92][93][94][95][96][97][98]…”