Improvements in computational accuracy of BRYNTRN (a baryon transport code)

摘要

Extension of BRYNTRN for use in space radiation dose analyses for very large shield thickness is made possible by improving the numerical algorithms. The efforts were concentrated in obtaining more accurate yet efficient interpolation and integration methods at each local computational step and in optimizing the grid distributions. A brief discussion of the nucleon transport theory and propagating formula is also given in conjunction with the analysis of error propagation which reveals the need for minimizing the local truncation errors. Sample calculations were made to verify the new algorithms. An accuracy of approximately 5 percent for a shield thickness of 150 g/sq cm was found when a minimal, thirty-point energy grid was used. This is far superior to the results obtained by using the old algorithms where the solutions can be of an order of magnitude different when a reasonable large number of grid points was used. The propagation step size which is restricted by the perturbation theory was re-evaluated to be in line with the improved numerical accuracy.