## 3 Results  
### Test of the Facility Performance  
During the design phase of the experimental setup, various simulations were conducted to evaluate the energy loss of the protons after the scattering on the Au target and the passage in the mylar window as well as the final spatial and energy distribution of the protons incident on the cellular samples and/or detectors used.  
In Figure 3, the comparison between the counts obtained on the SSBD detector positioned on the cell channel (15\({}^{\circ}\)) in the presence and in the absence of the mylar window (6 \(\upmu\)m thickness) is reported. SimNRA software (Max-Planck-Institut fur Plasmaphysik, Garching, Germany, [33]), was used to simulate the incident proton beam (beam diameter \(\mathcal{O}\) = 3 mm, 1 nA I for 60 s, 1050 keV proton energy), the layers' thickness and the detector geometry.  
As clearly shown, a 1050 keV monoenergetic proton beam is expected to yield on the detectors, and therefore on the cell sample, a spectrum centred at \(\approx\)685 keV, close to that corresponding to the maximum of the cross-section for the pB reaction (E\({}_{\text{max}}\) = 675 keV).  
Based on these results, a series of spectra for protons of E = 1050 keV obtained with the two SSBDs placed at 15\({}^{\circ}\) and 60\({}^{\circ}\) (Figure 2a) were acquired and a value of the R\({}_{60^{\circ}/15^{\circ}}\) between the counts of the two detectors was obtained; in Figure 4, an example is reported. Using the obtained value of the ratio and the count values of the spectrum at 60\({}^{\circ}\), the number of counts on the SSBD\({}_{15^{\circ}}\) or SSTD\({}_{15^{\circ}}\) CR-39, and therefore the dose to be used for the cell irradiation experiments, can be calculated, using Formulas (2) and (3).  
Figure 3: Simulated spectra obtained for the SSBD\({}_{15^{\circ}}\) using a proton beam of energy = 1050 keV, in the presence (red) or absence (blue) of a mylar foil (6 \(\upmu\)m thickness).  
For a current on the FC of 52.5 pA, a theoretical dose rate equal to \((1.91\ \pm\ 0.05)\cdot 10^{-2}\) Gy/s or \(1.15\ \pm\ 0.03\) Gy/min is obtained; dose rate values of this order are those commonly used in radiobiological experiments.  
Using this setup, two CR-39 SSTDs, positioned in place of the SSBD\({}_{15^{\circ}}\) (Figure 2b), were irradiated for two different exposure times; during the irradiation, the spectrum of the SSBD\({}_{60^{\circ}}\) was also acquired. Using the formulas reported in Formulas (2) and (3), the number of expected counts, hence the fluence/dose values, was estimated. The irradiated CR39 were then developed and scored; it was possible to observe the presence of a single family of tracks, homogeneous in diameter, which can therefore be associated with a single energy value (and LET). Moreover, the tracks appeared to be evenly distributed, for both detectors over the entire surface. A detailed count was performed by moving along the two main diagonals of the detectors. In Figure 5, the number of counts along the two diagonals for two SSTDs detectors together with the mean values are reported, while in Table 1 the obtained data are reported.  
The counts along the diagonals are distributed within 1 \(\sigma\) from the mean value, indicating that the chosen setup ensures a satisfactory beam homogeneity.  
The entire test experiment was repeated three times in three successive shifts obtaining comparable values for both proton energies on SSBDs and uniformity of track density distribution on SSTDs CR-39, with uncertainties lower than 2% and 5%, respectively.