Investigation of unexpectedly high-energy electron emission from water vapor by the impact of carbon ions with Bragg-peak energies and track analysis

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Further improving our previous apparatus, we have successfully measured absolute double differential cross section(DDCS) for secondary electron emission from water vapor by the impact of carbon ions with Bragg-peak energies. The angular distributions of DDCSs disagreed with the CDW-EIS theoretical calculation at the backward angles(> 100°), while single differential cross section(SDCS) agreed well with the CDW-EIS, particularly in the low-energy region(<200 eV), suggesting the contribution of Fermi-Shuttle acceleration to the ion-atom collisions is rather small for heavy-ion impact with incident energies of several MeV/u or higher. Comparisons of radial dose distributions for the carbon ions, deduced form Monte-carlo track simulation, with the Chatterjee model showed meaningful and significant discrepancies in the core region, implying the necessity of corrections of the model.