Novel simulation method of space charge effects in electron optical systems including emission of electrons

摘要

We present a comprehensive numerical method for iterative computation of electron optical systems influenced by space charge which can accurately describe all effects in an optical system, including areas near a cathode tip and all crossovers. We use two different algorithms of evaluating the space charge distribution in different parts of the system. The Monte-Carlo based particle-in-cell method is used in the vicinity of the cathode. The algorithm based on the calculation of the current density distribution from an aberration polynomial is used for the rest of the system. We introduce a re-meshing algorithm which adapts the finite element mesh used for the field calculation in each iteration to the actual space charge distribution to keep it sufficiently fine in all areas with non-zero space charge. The algorithm is finally tested on a design of an experimental electron-welding machine developed at the ISI of the CAS. (C) 2017 Elsevier B.V. All rights reserved.