## 2 Description of the Simulation Models and Experimental Set up
The main source of inconsistencies in Monte Carlo simulations are represented by the variance reduction techniques [35] usually employed for decreasing the simulation run time. Such method was not applied here. Scoring was performed using the Geant4 command line-based scoring system and a cylindrical mesh. The scoring mesh was binned in polar coordinates and had 5 degree angular and 0.2 cm radial steps, respectively. Proton, electron, and photon spectra, as well as their corresponding fluencies were assessed. The simulations were performed using a 32 core XENON E5-2650 with 20 GB RAM. The run time was approximately of \(70\pm 4\) h per simulation and the statistical fluctuations were less than 1%. The data were made available in a familiar web interface using Jupyter Notebooks [36]. This approach allowed for interactive data processing techniques to be applied to validate the simulation results. Thus, the output data files were easily integrated into other software packages for data analysis and further processing. Description of the Geometry Mesh of the Experimental Set-Up Used for Calculation of Radiation Dose Map Inside the Vacuum Chamber  
The simulation of radiation dose map was also performed with the Geant4 v.10.5 framework tools described above [25; 33; 34]. Firstly, the electron and proton sources were implemented into a mesh (see Figure 1) adapted to the specific parameters of the experimental set-up presented in Figure 2. The electron source (the first source of radiation) is illustrated as a yellow disk, the red disk represent the 5 \(\upmu\)m thick target behind which is positioned the proton source (the second source of radiation) designed as a green disk. The two sources were integrated into the simulation model using the GPS that allows the positioning of more than one source within an experimental set-up. Also, it was considered, that, the electrons that propagate in vacuum can generate nuclear reactions when interact with experimental set-up \begin{table}
\begin{tabular}{c c c} \hline \hline
**Source of Radiation** & **Electrons (Source 1)** & **Protons (Source 2)** \\ \hline Laser intensity (W/cm\({}^{2}\)) & \(5\times 10^{19}\) & \(5\times 10^{19}\) \\ Laser pulse duration (fs) & 40 & 40 \\ Laser spot area (\(\upmu\)m\({}^{2}\)) & 207 & 207 \\ Source radius (\(\upmu\)m) & 9 & 9 \\ Source position & ahead & behind \\ Angular distribution & \(4\pi\) & \(25^{\circ}\) half angle \\ Number of events & \(1.97\times 10^{12}\) & \(1.29\times 10^{9}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Characteristics of source terms. components (see Figure 2), producing secondary radiation such photons. For the considered particles energy range, in the simulation model, all available nuclear processes (in GEANT4 General Particle Source tools) were considered. The mesh of the experimental set-up was implemented using GEANT4 standard geometry components without any Boolean operations, and the overlapping regions were tested at the beginning of each run. The angular and energy spectral distributions of electrons, protons and photons obtained as result of the interaction of laser spot with the Ag target, as well as the geometry mesh from Figure 1, were used to simulate the radiation dose map inside the vacuum chamber. Figure 1: Geometry mesh of the GEANT4 simulation model: 1a—source of electrons; 1b—target; 1c—source of protons; 2—hole; 3—magnetic spectrometer; 4—target holder; 5—detector holder; 6—aluminum cylinder. The structure of the electron, proton sources and target are presented in the right corner of the image. Figure 2: (**a**) Experimental set-up; (**b**) Detailed of the experimental set-up.