Informatics

Modeling an electron gun with a focusing lens system with regard for space charge distribution

A. A. Klimakov

St. Petersburg State University, St. Petersburg 199034, Russian Federation

Abstract: The article focuses on modeling an electron-optical system taking into account the influence of space charge on the electron field emission. During the process of electron gun working around the edge the space charge is formed which can have strong influence on the emission of electrons. For such systems one of the main difficulties for the numerical calculation is that the radius of curvature at the edge of the cathode is different from the other elements by several orders. The system contains the field tip with the radius of curvature equal to $5$ nm and the system of oblique focusing lenses with oblique angle $40^\circ$. Poisson equation is used to solve the problem using a finite element method, Fowler–Nordheim relation helps to calculate the current, electron trajectories are calculated, the method of iterations helps to evaluate the influence of the space–charge. The impact of space charge on the current and on the electron scattering radius is evaluated. Bibliogr. 13. Il. 8.

Keywords: field emission, cold electron emission, space charges, oblique focusing lenses, Poisson equation, Fowler–Nordheim.

UDC: 533+537

Received: March 21, 2013