## 4 Discussion
This result is in agreement with the estimation of the water equivalent thickness of the sensor physical overlayers composed of a protective polyimide (approx. 0.5 mm) and aluminum (approx. 0.1 mm) and the 0.1 mm thickness of the substrate. The aluminum used for the electrical connections possesses a density different from that of the solid water, contributing to the measured EPOM value. Additionally, it should be considered that the edgeless diode collects charge from the rear of the die as well, suggesting that the EPOM may be positioned at least halfway between the top ohmic contact and the rear pn-junction. In a previous investigation, the shift in the EPOM for the PTW 60012 diode was 0.6 \(\pm\) 0.1 mm below its reference plane [46]. The output factor depicted in Figure 7 shows a close match with the CC04 IC, CC13 IC, and EBT3 readings. However, a slight under-response within smaller fields, not exceeding 2%, is present. which then gradually escalates to an over-response of 3% at a 20 \(\times\) 20 cm\({}^{2}\) field size. This good agreement is primarily attributed to the composition of packaging with low atomic number (Z) materials, such as Kapton, which minimizes the perturbation effects stemming from the packaging. The over-response with larger fields is well known for silicon devices and can be related to the fact that silicon diode sensitivity increased with low-energy photons arising from Compton's scattering, which increases with large fields [47; 48]. Conversely, the under-response in smaller fields may be linked to the dose rate dependence. Discrepancies might also arise from the potential misalignment of the edgeless array central pixel. Airgaps also play a fundamental role in the output factor of extremely small field sizes, which are difficult to completely remove during the experimental setup. The construction of the array may also introduce parasitic airgaps due to the superposition of protection overlayers of Kapton. Studies employing Monte Carlo simulations on optically stimulated luminescent dosimeters indicate that the introduction of air gaps upstream to the sensitive volume leads to a reduction in dose compared to scenarios without air gaps. Even an air gap of a mere 0.5 mm can cause an under-response exceeding 5% [49]. This effect becomes prominent primarily for small fields measuring below 18 mm, where electrons scattered out of the sensitive volume due to the presence of air are not compensated for due to the absence of lateral charge particle equilibrium (LCPE). The dose-rate dependence of the edgeless array for the DPP ranging from 0.03 mGy/pulse to 0.39 mGy/pulse is demonstrated in Figure 8. Normalizing the relative sensitivity of the edgeless array to an ionization chamber revealed a variation of \(\pm\)2% of all the p-type edgeless diodes across the 0.12 to 0.39 mGy/pulse range, covering the dose rates typically used in SRS; however, lower dose rates will need to be corrected, since an underestimation of the dose up to 15% for the DPP was observed with dose rates lower than 0.1 mGy/pulse. Previous studies on different structures of p-type edgeless diodes have demonstrated similar results for DPP variation [28; 31]. Notably, PP diodes exhibit a reduced and more consistent dependence on DPP compared to NN diodes. The established literature strongly favors pre-irradiated p-type diodes over n-type due to their flattened dose rates [50; 51; 52]. The dose rate dependence can be related to the correlation between the minority carrier lifetime and several other factors: irradiation history, resistivity, as well as the concentration and energy levels of recombination-generation (RG) centers within the band gap. According to the Shockley-Read-Hall theory, a super-linear response is anticipated at high dose rates of pulse LINAC beams, owing to the comparable excess concentration of minority charge carriers to the equilibrium majority concentration. This increased minority carrier lifetime at higher dose rates contributes to the observed super-linear response [50; 52].