Judging the reliability of stopping power tables and programs for protons and alpha particles using statistical methods

Abstract

Using our large collection of experimental electronic stopping power data for H and He ions in elemental targets, we compare these data to theoretical programs by Grande and Schiwietz and by Sigmund and Schinner; and to semi-empirical tables by Northcliffe and Schilling; Andersen and Ziegler; Janni; Ziegler, Biersack and Littmark; ICRU; and Ziegler. We use a statistical method; every comparison is characterized by a mean normalized difference Δ and by its standard error σ. While Δ describes the systematic difference between table and data, σ provides information about the experimental errors. As an example, we discuss the energy loss of H ions in Al in detail. Considering all targets, we find that the recent program SRIM 2003 by Ziegler describes the data better than all other (older) programs. Averaging over all targets and energies, the accuracy of SRIM is about 7–8% for solids and 3–4% for gaseous targets; for the theoretical programs, we see a tendency for small systematic deviations. Some apparently unreliable measurements were rejected from the analysis. Two low energy measurements for H ions in He had to be excluded because of very large discrepancies due to the threshold effect.