## 5 Results: Mass, Charge, and Energy Distributions of Secondary Particles  
Figure 4 shows the yield of secondary particles as a function of the atomic and mass numbers (Z and A, respectively) produced in the proton-Nomex interaction. Since the production rates depend on the processes that open with the increase of proton energy, we investigate how the production of secondary particles evolves with the bombarding energy. We selected a few energy values within the energy spectrum of GCRs shown in Figure 1 to give an overview of such evolution. At all energies, in the calculation results, we can identify three main production clusters located (1) at the larger masses around the mass of \({}^{37}\)Cl, (2) around the masses of \({}^{12}\)C and \({}^{14}\)N, (3) in correspondence of the light-particle masses with atomic number Z \(\leq\) 2. The presence of these three clusters provides the first indication that protons impinging on C, N, and Cl nuclei produce composite systems, as a consequence of the proton capture that deceive by emitting light particles in a cascade. Particle emission can be evaporation-like (producing a Maxwellian energy spectrum, more likely at the lowest proton energy) or of the pre-equilibrium type (with a non-Maxwellian energy spectrum extended up to almost the beam energy). The mass range or width of clusters 2 and 3 depend on the excitation energy and increase with the proton energy. Such a trend is expected since the highest the excitation energy, the more particles are evaporated, and the lightest is the residual nucleus. As a consequence, on the light particle side (cluster 3), the increase of the excitation energy opens more decay channels, decay cascades are longer, and deuterons, tritons, and \({}^{3A}\)He emissions become more probable. Such an increase is clearly visible in Figure 4. The relative population of the ions that differ by one unit of mass and charge from \({}^{12}\)C, \({}^{14}\)N, and \({}^{37}\)Cl can also slightly change because direct reaction channels are opened at larger proton energy. However, this effect is limited to such mass and charge regions since protons can only produce knockout of protons or neutrons or \begin{table}
\begin{tabular}{c c c} \hline
**Target** & **Thickness (cm)** & \(\rho\) **(g/cm\({}^{3}\))** & **Composition** \\ \hline _Nomex_ & 17.4 & 1.15 & [H(4\%)C(54\%)N(9\%)O(10\%)Cl(23\%)]45\% + [N(70\%) O(30\%)]55\% \\ \hline \end{tabular}
\end{table} 
Table 1: Thickness, density, and composition of the Nomex target used as a shield in space. \begin{table}
\begin{tabular}{c c} \hline
**Particles** & **Models** \\ \hline \(e^{-}\), \(e^{+}\), \(\gamma\) & Penelope \\ \hline _Protons_ & CHIPSElastic, Bertini, Binary \\ \hline _Neutrons_ & HP Elastic, LElastic, CHIPSElastic, HP Inelastic Model, Bertini, Binary \\ \hline _Ions_ & Binary \\ \hline \end{tabular}
\end{table} 
Table 2: The models implemented in the Geant4 package and used in the DOSE application. Default parameters are used. a pickup of a neutron. Thus, the production of secondary protons and neutrons can also have a slight contribution from these direct channels. The extension of clusters 2 and 3 towards smaller masses and charges reaches saturation at energies above 200 MeV because the wavelength of the relative motion becomes so small that nuclei are transparent to protons and productions of different particles (e.g., muons, pions, etc.) become the predominant channels via inelastic direct channels such as p-p and p-n. This behavior is also reflected in the spectra of the atomic number of the secondary fragment in Figure 5 and in the energy spectra shown in Figure 6. The energy spectra are dominated at the lowest energies by light particles, as, for instance, the emission from compound nuclei, while direct reactions are the dominant production processes at all beam energies. The energy spectra are consequently of continuous type.