Measurements of the mean energy-loss of swift heavy ions in carbon with high precision

Abstract

Z 1 dependent effects in heavy ion stopping around stopping maximum under conditions of equilibrium charge have been measured with a time of flight-energy elastic recoil detection analysis (ToF-E ERDA) set-up. The ToF section was used to tag individual recoil atoms with their energy prior to entering the stopping foil and the exit energy was measured subsequently using a Si p–i–n charged particle detector. The mean energy-loss and average energy of recoils have been determined for many elements with Z 1=3–26 in a continuous energy range from ∼0.2 to ∼0.9 MeV per nucleon and from ∼0.03 to 0.1 MeV per nucleon for 79Au. The stopping power and energy dependence were in good agreement with most literature data. However, considerable discrepancies in the energy dependence were observed with semi-empirical SRIM-2000 estimates around the stopping power maximum for some of the elements. This technique, which allows direct measurement of Z 1 effects in stopping foils to be performed with high-precision, showed that the dependence of the experimentally determined stopping number ( L exp) with the stopping parameter ξ clustered around a trend line with Z 1 dependent deviations that exceeded the estimated uncertainty. The deviations were more significant for large ξ and were 15% between 9Be and 7Li at ξ=10.