## 5 Results
### Energy Calibration and Dead Layer Estimation
The interpolated data points (black squares) are computed according to Equation (8), which takes into account the average number of pixels per cluster, taken from \[E_{dep}\ [\mathrm{keV}]=(598\pm 68)\ [\mathrm{keV}]-(51.5\pm 5.8)\frac{1}{ \cos\theta}\ [\mathrm{keV}], \tag{6}\]1  
Having found that saturation effects at pixel level begin between 500 and 600 ToT [25 ns] units, one can further analyze the broadened ToT volume peak observed in Figure 10 for 5.6 MeV alphas. Following a method used in [22], the left graph in Figure 15 presents the breakdown of the distribution of the cluster ToT volume for 5.6 MeV alphas, divided into four categories based on the number of \"hot\" pixels that are exceeding a ToT threshold set to 565 [25 ns] units. Since one can assume with good approximation that all alphas are depositing an equivalent amount of energy in the sensor, it is reasonable to associate these categories to a variable degree of charge sharing between the central pixels, linked to the position of the alpha particle hit within the struck pixel. In practice, when the hit occurs in the centre of a pixel, a larger fraction of the released charge remains within its boundaries, leading to a single hot pixel in the cluster, whereas if the hit occurs close to a pixel boundary, the charge sharing is enhanced, resulting in up to four hot pixels. As Figure 10 clearly shows that the distribution with only one hot pixel presents a lower mean cluster ToT compared to the others, it is fair to attribute the shift to a higher level of saturation in the central pixel, due to the higher fraction of alpha energy which is deposited into it, while this interpretation involves hypotheses that cannot be easily verified in the data, it provides interesting insights into the origin of the broadening of the cluster ToT peak of 5.6 MeV alphas, linking it directly to saturation effects. Lastly, it is thorough to investigate why the level of saturation observed for protons in Figure 13 is larger than the one for alphas. As a first step, one can compare the cases of 3 MeV protons and 2.96 MeV alphas in Table 1, noting that despite a larger fraction of energy lost in the front layers (which results in less energy being measured by the sensor), the alphas result in slightly larger clusters (22.5 average pixels per cluster versus 21.9). An explanation of this feature stemming from the charge collection within the silicon detector is that the alpha hits lead to more charge sharing amongst pixels as opposed to protons with similar kinetic energy. This is presumably due to their different linear energy transfer (LET), leading to a different distribution of the energy deposition in the active volume of the sensor (visible in Figure 4), ultimately leading to different ranges in silicon. In turn, a difference in the amount of charge sharing determines the level of saturation at the pixel level, leading to the observed differences between proton and alpha runs. To further verify this, the right graph in Figure 15 presents the distribution of the time-of-arrival (ToA) of the pixel hits, measured with the fToA timing resolution of 1.5625 ns, for clusters formed by 3 MeV protons and alphas (recalling that the actual energy deposited  
\[E_{dep}\ [\mathrm{keV}]=(598\pm 68)\ [\mathrm{keV}]-(51.5\pm 5.8)\frac{1}{ \cos\theta}\ [\mathrm{keV}], \tag{6}\]2 (**a**) Distribution of cluster ToT volume for 5.6 MeV alphas with variable number of pixels exceeding a threshold set to 565 [25 ns] ToT units, and (**b**) distribution of pixel ToA in 3 MeV proton and alpha clusters, where the bin at ToA = 0 corresponds to the first pixel that is hit, and the bin width is set to four times the fToA timing resolution of 1.5625 ns. in the active volume is lower than the beam energy, especially for alphas, as shown in Table 1). Since most of the charge is deposited closer to the front layer (and further from the collection electrode) for alphas (due to the shorter range at the same energy) than for protons, the charge collection time is also larger.