B ELSEVIER Nuclear Instruments and Methods in Physics Research B 134 (1998) 1-12 A study of primary electron charge deposition near the surface of a target by Monte Carlo simulation Valentin Lazurik, Vadirn Moskvin * Radiation Physics Laboratory, Kharkov State University, P.O. Box 60, 310052 Kharkov, Ukraine Received 16 July 1996; received in revised form 15 September 1997 Abstract The Method of Trajectory Rotation [V. Lazurik, V. Moskvin, Nucl. Instr. and Meth. B 108 (1996) 276] is modified to compute the charge deposition density and the yield of an electron spectrum at given depths of targets irradiated by electron beams. Primary electron charge deposition near the boundaries of finite targets is studied. It is found that the depth-profiles of the primary electron charge deposition have a drastic nonlinear decrease near the target vacuum interface. The theoretical description of the charge deposition near the inhomogeneity in a target is discussed. The elec- tion of model parameters, i.e., the cutoff energy and the depth bin width, for accurate computer simulation with the use of the conventional Monte Carlo techniques is considered. © 1998 Published by Elsevier Science B.V. PACS: 78.70.-g; 34.50.Bw; 87.53.Fs; 81.40.Wx Keywords: Electron transport; Computer simulation; Monte Carlo techniques; Primary electrons; Charge deposition; Stochastic wandering; Target-vacuum interface; Boundary effect; Electron spectrum 1. Introduction Data on quantities describing the action of fast electrons on materials are necessary for the analy- sis of the electrophysical processes in objects irra- diated by electron beams. The energy and charge deposition density are the fundamental quantities used in such analysis. At present, the computer simulation of electron transport with the use of Monte Carlo techniques *Corresponding author. 0168-583X/98/$19.00 © 1998 Published by Elsevier Science B.V. All PIISO168- 58 3X(97)O0510-7 is the basic method of obtaining these data. The general purpose Monte Carlo codes, such as ITS [1], GEANT [2] and EGS [3], are widely used in practice. What all these codes have in common is that the transport of electrons is simulated for a re- gion of their energies from an initial energy/:~ to a given cutoff energy gmin. It is assumed that elec- trons deposit their charge at the end of their tracks. Tracing the trajectories of electrons until the energy Emin is connected with the limits of va- lidity of the physical models used in computation. Thus the cutoff energy is a model parameter that defines an accuracy of simulation. Notice that rights reserved.