Energy loss of protons in carbon nanotubes: experiments and calculations

We have studied the energy loss of protons in multi-walled carbon nanotube (MWCNT) samples, both experimentally and theoretically. The experiments were done in transmission geometry, using 6 and 10 keV proton beams, with the MWCNT targets dispersed on top of a ∼20 nm-thick holey carbon coated TEM grid (amorphous carbon film, a-C). The energy loss of protons interacting with the MWCNTs and the amorphous carbon film is obtained after analyzing the signals coming from both types of carbon allotropes. The electronic energy loss of protons is calculated using the dielectric formalism, with the target energy loss function built from optical data. Comparison of experimental and theoretical data indicates that model calculations appropriate for three-dimensional (bulk) targets substantially overestimate the energy loss to MWCNTs. In contrast, a recent parameterization of the dielectric function of MWCNTs predicts significantly lower stopping power values compared to the bulk models, which is more in line with the present experimental data when considering the additional stopping mechanisms that are effective in the keV range.This work has been financially supported by the European Union FP7 ANTICARB (HEALTH-F2-2008-201587), Financiamiento Basal para Centros Científicos y Tecnológicos de Excelencia, CEDENA, FONDECYT Grants 1071075, 1070224 and 7070175, Grant USMDGIP 11.04.23, CONICYT/Programa Bicentenario de Ciencia y Tecnología (CENAVA) PBCTACT027, Millennium Scientific Initiative and the Spanish Ministerio de Ciencia e Innovación (Projects FIS2006-13309-C02-01 and FIS2006-13309-C02-02). CDD thanks the Spanish Ministerio de Educación y Ciencia and Generalitat Valenciana for support under the Ramón y Cajal Program