## 3 Results
### MOS_kin Linearity and Track Spacing_  
With corrected film measurements, the MOS_kin_ exhibits a linear response to total absorbed dose with increasing DPP, as well as large doses delivered within a single pulse. Shown in Figure 7, the slope of the fitted line, 3.386 \(\pm\) 0.022 mV/cGy, corresponds to the sensitivity of the MOS_kin_s within the 100 MeV electron irradiation environment at PEER. This is in the vicinity of other results in the literature when the incident field is electrons in the MeV range [41; 45]. The magnitude is higher; however, the MOS_kin_s used in this study have a thicker gate oxide than those of other studies. The MOS_kin_ sensitivity is proportional to the square of the gate oxide thickness and applying this factor to the results of this study places the sensitivity in the expected range. To confirm the MOS_kin_ response is valid, the sensitivity was also checked in a 20 MeV electron field using a Varian Truebeam linac at St. George Hospital in Sydney, Australia. The temporal structure of the linac pulses are orders of magnitude different from that of PEER and are summarised in Table 1. The results of the calibration are also seen in Figure 7. The slope of the linear fit is 3.761 \(\pm\) 0.003 mV/cGy, an increase in sensitivity of about 11%, within the expectations relative to PEER.  
Figure 6: The correction curve established for the EBT-XD film. The mean normalised response of the 20 pulse deliveries, 0.003997 Gy/pC shown in Figure 5, was used to calculate the predicted dose for the measured charge during each film exposure.  
The highest single pulse delivery was 22.73 Gy, consisting of 100 bunches, at an instantaneous dose rate within a bunch of \(2.273\times 10^{9}\) Gy/s, and average dose rate of \(1.14\times 10^{8}\) Gy/s. A single bunch is delivered in 100 ps, and hence, we consider the DPB for comparison against the Geminate model, as this is the shortest structure of the PEER beam. At 0.23 Gy/bunch, well below the limiting case for the Geminate model, the spacing between the incident tracks calculated using Equation (3) is 385 nm. At a factor of 24 greater than 16 nm, the required separation for 100 MeV electrons, it can be assumed that the overlap of electrons between neighbouring tracks has not invalidated the application of the Geminate model. Therefore, the absorbed dose remains proportional to the number of incident tracks, and the linear response of the MOS_kin_ to increasing DPP is, therefore, as expected.  
\begin{table}
\begin{tabular}{c c c} \hline  & **Varian Truebeam** & **PEER** \\ \hline Bunch Length & Unknown & 100 ps \\ Pulse Length & 3–5 μs & 20–400 ns \\ DPP & \(\sim\)10\({}^{-3}\) Gy & 1–23 Gy \\ Max Average Dose rates & \(\sim\)10\({}^{1}\) Gy/s & \(\sim\)10\({}^{8}\) Gy/s \\ \end{tabular}
\end{table}
Table 1: Comparison of typical Varian Truebeam pulse structures and dose rates against PEER. Clinical values adapted from [89]. The DPP stated for PEER reflects the values used in this investigation. It is envisioned however, that an increase of at least twice is feasible in the current configuration with varied delivery parameters.  
Figure 7: The MOS_kin_ exhibited a linear response across all levels of DPP, whether accumulated during increasing levels of dose, or through large, single pulses. The slope of the linear fit, representing the sensitivity of the MOS_kin_ within the PEER field is 3.386 \(\pm\) 0.022 mV/cGy. Ratios of electron–hole pair spacing between 20 MeV and 100 MeV fields predicted an 8% increase in sensitivity. The sensitivity of the MOS_kin_ within the 20 MeV clinical field is 3.761 \(\pm\) 0.003 mV/cGy, approximately 11.1%. All MOS_kin_ uncertainties are one standard deviation. The dose uncertainty for the VHEE exposure propagates with the correction curves and is applied to the standard deviation of raw film measurements. Clinical dose deliveries are highly regulated, uncertainties are 1% of the prescribed dose.