Numerical Simulation of Beam Formation and Transport in an Electron Gun for Different Applications

Abstract

A Pierce-type electron gun with spherical anode has been numerically co mputer-aided analysed to yield an appropriate beam with suitable properties valid for d ifferent applications. It has been proven that, around a certain value of the aspect ratio, 0.75, the resultant beam geometry could be suitably controlled. The gun geometry plays an important role for beam shaping; parallel, converged or diverged. The min imu m electric field required to prevent beam expansion due to space charge effect has been estimated and it is found to be proportional to the cubic root of the d istance fro m the anode to the target (Z 1/3 ). Also, it is proved that the minimu m beam radius is realized at the minimu m beam perveance and the maximu m beam convergence angle. As a result, this reveals that, the gun geometry controls the beam emittance. The gun design analysis proposed here helps to choose the better operating conditions suitable for low energy electron beam bo mbard ment and/or injection applications.

Effect of the Gap Size between the Cathode and the Wehnelt Cylinder Bore on the Emittance of the Thermionic Electron Gun

“…By heating a small cathode element, the cathode can generate a cloud of electrons through thermal emission; this is accelerated to form an electron beam. Before a package is introduced into a system, it is critical to have complete information about its emittance, which is an important quantity to consider; it is the most important factor in producing a high-quality electron beam [5]. Electron guns can operate in two modes: continuous and pulsed.…”