## 3 Results and Discussion
Figure 6: Microdosimetric \(yd(y)\) distributions measured using cathode walls loaded with varying concentrations of \({}^{10}\)B. The solid black line represents the total distribution, encompassing both gamma and neutron components. In contrast, the colored lines represent the pure BNC components only. (a) 10 ppm of \({}^{10}\)B; (b) 25 ppm of \({}^{10}\)B; (c) 70 ppm of \({}^{10}\)B; (d) 100 ppm of \({}^{10}\)B.  
Figure 8: Microdosimetric BNC components of the \(yd(y)\) distribution for cathode walls with varying concentrations of \({}^{10}\)B. The thin fluctuating lines represent the direct measurements. The thick lines represent the components evaluated at the concentrations of 10, 25, and 70 ppm of \({}^{10}\)B, scaling the single component measured at 100 ppm of \({}^{10}\)B.  
Figure 7: **Top panel**: the relative increase in the total number of events (red filled circles) and dose (green empty circles) as a function of \({}^{10}\)B concentration. Both enhancements are plotted relative to their values in the absence of \({}^{10}\)B. The lines are the linear best fit of experimental data (same colors as the symbols). **Bottom panel**: relative residuals with respect to a zero-intercept linear fit of experimental data. Figure 9 depicts a comparison of the BNC component measured in this work at a simulated site size of 1 \(\upmu\)m with the corresponding component measured and calculated by [PERSON] at a 2 \(\upmu\)m site [6] and by [PERSON] [10] and [PERSON] at a 0.5 \(\upmu\)m site [11]. The agreement between the curves is very good, and small discrepancies are consistent with the variations in site sizes, gas, and shape of the sensitive volume (SV). The three main relative dose components of the investigated radiation field, namely \(D_{\text{ph}}/D_{\text{tot}}\) (relative photon component), \(D_{\text{n}}/D_{\text{tot}}\) (relative neutron component), and \(D_{\text{BNC}}/D_{\text{tot}}\) (relative BNC component), at various boron concentrations, are reported in Table 1.  
Spectral \(yd(y)\) distributions were derived from the 100 ppm data for boron concentrations of 8.5 ppm and 30 ppm, representing typical average concentrations in BNCT for healthy and tumoral cells, respectively. These distributions are presented in Figure 10, along with the distribution without boron. The right panel of Figure 10 displays dose distributions weighted by the Tilikidis weighting function [25]. Application of the weighting function enhances the impact of the BNC component compared to the photon component. The absorbed dose, normalized to a nominal dose of 1 Gy delivered in the case of no boron enrichment, RBE values calculated using Equation (3), and the biological-weighted dose are reported in Table 2 for various boron concentrations. \begin{table}
\begin{tabular}{c c c c} \hline
**10B** **Concent/ppm** & \(D_{\text{ph}}\)/\(D_{\text{tot}}\) & \(D_{\text{n}}\)/\(D_{\text{tot}}\) & \(D_{\text{BNC}}\)/\(D_{\text{tot}}\) \\ \hline
0 & 0.85 & 0.15 & 0 \\
10 & 0.79 & 0.21 & 0.074 \\
25 & 0.71 & 0.29 & 0.175 \\
70 & 0.55 & 0.45 & 0.36 \\
100 & 0.49 & 0.51 & 0.43 \\ \hline \end{tabular}
\end{table} 
Table 1: The three main relative dose components at various \({}^{10}\)B concentrations. Figure 9: Microdosimetric BNC components of the \(yd(y)\) distribution measured in this work, compared with those measured by [PERSON] [6], [PERSON] [10] and [PERSON] [11]. It is worth noting that higher RBE values could potentially be attained by reducing the gamma component using appropriate shielding in the MUNES beam-shaping assembly. Figure 10 illustrates that a differential boron concentration of 8.5 ppm in healthy tissue and 30 ppm in the tumor leads to a dose enhancement for cancer cells of approximately 14%. This enhancement is primarily attributed to high linear energy transfer (LET) alpha particles and Li ions, which have larger relative biological effectiveness (RBE) values. As a result, the RBE-weighted dose experiences a significant increase of 33%, playing a pivotal role in the curative effect of boron neutron capture therapy (BNCT).