The code “OPTICS-3” for 3D problems of electron optics

The computer code “OPTICS-3” is based on use the Boundary Element Method (BEM) [1] for the field evaluation in complex-shape three-dimensional domains, and Principal Ray Method (PRM) (Grinberg, 1948) for the trajectory analysis. The PRM represents the wide beams with a few trajectories which are used as the curvilinear axes to make the 3-rd order aberration expansions in their vicinities. Those expansions need evaluation the high-order field derivatives up to fourth order. Thus, the combination of BEM and PRM gives the possibility to provide precision optic calculations, and substantially reduce the amount of computations comparatively with the numerical integration of Lorentz´s motion equations. The necessity of taking into account the electric and magnetic fields excited by the beams creates non linear self-consistent problem, which is solved with iteration procedure. The perspective Grinberg´s approach was not realized before for full three-dimensional electron optical systems, probably because of the complexity of its mathematical apparatus. Earlier successful realizations of aberration approach for two-dimensional problems of emission electron optics were presented in publications (Ivanov, 1981) for the code “OPTICS-2”, (Kulikov, 1996) for the code “ELIM-E” and (Andreev et al., 2002) for the code “ELIM-D”. Here we present the first version of such computer code “OPTICS-3”, and some results of numerical simulations of electron gun for the 75 MW sheet-beam klystron with this code.