Zero-degree measurements of ${}^{12}\mathrm{C}$ fragmentation at 95 MeV/nucleon on thin targets

During therapeutic treatments using ions such as carbon, nuclear interactions between the incident ions and nuclei present in organic tissues may occur, leading to the attenuation of the incident beam intensity and to the production of secondary light charged particles. As the biological dose deposited in the tumor and the surrounding healthy tissues depends on the beam composition, an accurate knowledge of the fragmentation processes is thus essential. In particular, the nuclear interaction models have to be validated using experimental double differential cross sections which are still very scarce. An experiment was realized in 2011 at GANIL to obtain these cross sections for a 95-MeV/nucleon carbon beam on different thin targets for angles raging from 4${}^{\circ }$ to 43${}^{\circ }$. To complete these data, a new experiment was performed in September 2013 at GANIL to measure the fragmentation cross section at zero degree for a 95-MeV/nucleon carbon beam on thin targets. In this work, the experimental setup will be described, the analysis method detailed, and the results presented.

Figure 1

Schematic view of the experimental setup.

Figure 2

(a) and (b) $\Delta$ E/E maps without any selection. (c) $\Delta$ E/E map cleaned up from $①$. (d) CsI fast/slow map cleaned up from $①$. (e) CsI fast/slow map cleaned up from $①$ and $③$. (f) Final $\Delta$ E/E map resulting in the combination of graphical cut $①$–$④$.

Figure 3

Energy distribution of ${}^4\mathrm{He}$ and ${}^7\mathrm{Li}$ fragments for the carbon and titanium targets. The two highlighted regions correspond to the experimental energy thresholds (gray shading; cf. Table 3) and to the energy range of the beam when passing through the target (red shading).

Figure 4

${}^4\mathrm{He}$ angular distributions for the hydrogen (a) and titanium (b) targets. The distributions have been fitted with two functions. The first one (red lines) resulting from the sum of a Gaussian and an exponential function and the second one (blue lines) resulting from the sum of two exponential functions.

Figure 5

${}^4\mathrm{He}$ angular distributions for the hydrogen (a), carbon (b), aluminum (c), and titanium (d) targets. The distributions have been fitted with a function resulting in the sum of a Gaussian and two exponential functions.

Figure 6

Angular distributions of ${}^4\mathrm{He}$ (a), ${}^7\mathrm{Li}$ (b), and ${}^7\mathrm{Be}$ (c) obtained for the carbon target. The distributions have been fitted with a distribution resulting in the sum of a Gaussian and two exponential functions.