ISICSoo: A class for the calculation of ionization cross sections from ECPSSR and PWBA theory

Abstract

ISICS, originally a C language program for calculating K-, L-and M-shell ionization and X-ray production cross sections from ECPSSR and PWBA theory, has been reengineered into a C++ language class, named ISICSoo. The new software design enables the use of ISICS functionality in other software systems. The code, originally developed for Microsoft Windows operating systems, has been ported to Linux and Mac OS platforms to facilitate its use in a wider scientific environment. The reengineered software also includes some fixes to the original implementation, which ensure more robust computational results and a review of some physics parameters used in the computation. The paper describes the software design and the modifications to the implementation with respect to the previous version; it also documents the test process and provides some indications about the software performance. Ionization and X-ray production cross section calculations for ion-atom collisions. Solution method: Numerical integration of form factor using a logarithmic transform and Gaussian quadrature, plus exact integration limits. Reasons for the new version: Capability of using ISICS physics functionality in other software systems; porting the software to other platforms than Microsoft Windows; improved computational robustness and performance. Summary of revisions: Reengineering into a C++ class; several internal modifications to improve correctness and robustness; updated binding energies tabulations; performance improvements. Running time: The running time depends on the selected atomic shell and the number of polynomials used in the Gaussian quadrature integration.

Evaluation of Atomic Electron Binding Energies for Monte Carlo Particle Transport

“…This version, which was used to produce the data for this paper, involves new implementations of some parts of the ISICS code, which contribute to the numerical correctness and computational robustness of the software. The new features and verification of this new version of ISICS are documented in [170]. The experimental validation of cross sections generated by this new version of ISICS produces consistent results with those reported in [43], when the two code versions are run in the same configuration.…”

“…The PWBA and ECPSSR cross section tabulations distributed with the Geant4 code were produced with the ISICS 2008 version, which uses the Bearden and Burr binding energies. Recent updates to ISICS [49] offer the option of using Williams' compilation of binding energies as alternative values to the default Bearden and Burr's ones; a further evolution of ISICS [170] lets the user specify an arbitrary source of atomic binding energies, thus providing access to any of the options analyzed in this paper. This version, which was used to produce the data for this paper, involves new implementations of some parts of the ISICS code, which contribute to the numerical correctness and computational robustness of the software.…”

Energy loss in the ECPSSR theory and its calculation with exact integration limits

“…Table 1. Comparison of the eCPSSR cross sections for K-shell ionization by protons as tabulated in ERCS09 [23] and evaluated with the ISICS code [24,25] and our code with the wrong (equation 13 For the algorithm that applies the inverted sequence of integration over W and Q, the integration limits are given in [30]. As the expressions [30] consider the PSS effect implicitly (assuming that the parameter θ S had already been multiplied by ζ S ), we rewrite these equations including the parameter ζ S explicitly:…”

“…It was even believed that all codes using exact integration limits are incorrect and that only the original ECPSSR theory using the f S -function should be used [22]. Despite explicit warnings [16,21,22] about incorrect implementation of the ECPSSR theory, present computer codes such as ERCS08 (this acronym stands for electron removal cross sections) [23] and the latest edition of ISICS [24,25] continue to be in error. The reliance on these codes may give the wrong impression about the efficiency of the ECPSSR model, especially when it is compared with different empirical and semiempirical fits to the inner-shell ionization data [26].…”

PIXE simulation: Models, methods and technologies

“…This approach represents approximately an order of magnitude improvement in computational speed with respect to direct calculation of theoretical formulae in the course of the simulation. The tabulations of theoretical cross sections have been produced by means of the ISICS [32] code, which has been reengineered into a C++ class [33] for improved versatility of use.…”