Stopping powers and energy distributions of fission fragments in gases

Abstract

The electronic stopping power of CO, CO 2, O 2, CF 4, CF 2Cl 2 and SF 6 has been experimentally determined in the range of fission fragment energies (0.01–1.0) MeV/amu. Based on Bragg's rule of additivity and using experimental data the stopping power of C, F, Cl and S has been calculated. As distinct from the theory of Lindhard resulting in a linear velocity dependence of the electronic stopping power ( dE dx ) e for ions, in the case of fission fragment stopping the experimental values ( dE dx ) e are shown to obey a non-linear electronic stopping power behaviour. Brice's semi-empirical equation for ( dE dx ) e accurately describes the experimental data obtained, and the values ( dE dx ) e tabulated by Northcliffe and Schilling may serve only to estimate the quantities in the case of fission fragment deceleration. A study was made of the change in the mean-squared deviations of energy distributions of light and heavy groups of fission fragments on their stopping in the above gases and it is shown that their estimation may be made using the equation previously derived by the authors.