Abstract
Measured charge- and mass-changing cross sections for the systems $^{4}\mathrm{He}+^{12}C$, $^{4}\mathrm{He}+^{16}O$, $^{4}\mathrm{He}+^{28}\mathrm{Si}$, and $^{4}\mathrm{He}+^{1}\mathrm{H}$ in the energy range $70--220\phantom{\rule{4pt}{0ex}}\mathrm{MeV}/\mathrm{u}$ are presented. The cross sections were obtained via the attenuation method where a $\mathrm{\ensuremath{\Delta}}E\text{\ensuremath{-}}E$ scintillator telescope was used for particle identification. These new data have particular relevance for future applications of $^{4}\mathrm{He}$ ions in ion-beam radiotherapy because this technique relies on precise heavy ion transport models for an accurate dose calculation. The radiation transport codes applied for this purpose typically make use of parametrizations of the total reaction cross section ${\ensuremath{\sigma}}_{R}$. The widely used parametrization for nucleus-nucleus reaction cross sections by Tripathi et al. is shown to underpredict the new experimental cross sections for $^{4}\mathrm{He}$ ions in the therapeutic energy range by up to $30%$, which can lead to considerable dose calculation uncertainties. Therefore, modifications of the parameters in the Tripathi model are proposed to optimize it for applications related to $^{4}\mathrm{He}$ ion-beam therapy.
Highlights
An essential quantity for heavy ion transport calculations is the total reaction cross section σR, which gives the probability for an inelastic nuclear reaction to occur [1,2]
The widely used parametrization for nucleus-nucleus reaction cross sections by Tripathi et al is shown to underpredict the new experimental cross sections for 4He ions in the therapeutic energy range by up to 30%, which can lead to considerable dose calculation uncertainties
Measurements of charge- and mass-changing cross sections for the systems 4He + 12C, 4He + 16O, 4He + 28Si, and 4He + 1H in the energy range 70–220 MeV/u were performed. These data are relevant for future radiotherapy applications of 4He ion beams as planned at the Heidelberg Ion-Beam Therapy Center (HIT)
Summary
An essential quantity for heavy ion transport calculations is the total reaction cross section σR, which gives the probability for an inelastic nuclear reaction to occur [1,2]. The cross section predictions obtained from these parametrizations are most realistic for colliding systems which are well characterized by experiments. For unexplored systems their predictions might still be reasonable due to the underlying systematics, but for projectile-target combinations of special interest it is preferable to check the models against measured cross sections. The total reaction cross section σR is difficult to measure directly because target fragments have very low energies and are hard to detect. Typical measured quantities which can serve as an estimate for σR are the charge-changing cross section σ Z (projectile loses at least one proton) and the mass-changing cross section σ A (projectile loses at least one nucleon), considering that most nuclear reactions lead to fragmentation of the projectile
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