A general framework for numerical calculation of properties of charged-particle optical systems

This paper describes a new algorithm for calculating system properties which can deal with the diversity of designs and design questions encountered in charged-particle optical (CPO) system design. Our approach for calculating properties of CPO systems is to combine the generality of direct ray tracing with the modularity of the matrix multiplication methods. The system is defined in terms of a sequence of components whose properties can be described in terms of aberrations, transfer maps or even look-up tables. Test particles, defined by their position in phase space, are tracked from component to component through the system. Aberration coefficients of the system are calculated by means of fitting the coefficients of a transfer map to the phase-space coordinates of the particles.