## 3 Results and Discussions  
1. Simulation Results on the Angular Spectral Distribution of Electron, Proton and Photon Beams Generated in TNSA Regime  
Laser accelerated electron and proton beams in vacuum are the primary sources of radiation in a high power laser-thin solid target interaction experiment in the TNSA regime. The secondary radiation source consists mainly of bremsstrahlung X-ray photons or gamma rays both produced by the interaction of hot electrons with target nuclei. The interaction of primary radiation, (mainly of electrons) with the vacuum chamber walls and detectors placed at different distances and inclination angles with respect to the laser-target interaction point, also generate bremsstrahlung radiation on a nanosecond time scale. The opening angle of proton and electron accelerated beams depend on few parameters such as: target thickness, laser intensity, laser focal spot size, emittance, and source dimensions [1, 2, 3, 4, 5, 6]. Many authors [1, 2, 4, 5, 6, 7, 45, 46, 27] reported that electron and proton beams generated in TNSA regime have the highest number and energy in forward direction, normal to the target. The decrease of protons energy with the increase of opening angle was reported both by calculations and experimental measurements [9,45]. The spectra of proton and electron accelerated beams as well as of the emitted photons calculated using the simulation model described above (without considering the mesh of the experimental set-up  
Figure 3: (**a**) Pixel values to optical density Rodbard calibration curve. (**b**) The dependence of optical density on radiation dose. presented in Figure 1) allowed us to find angular and energy distributions of primary and secondary radiation (see Figures 4 and 5). Within 0-15 degrees of angle, the spectra of electrons, protons, and photons are shown in Figure 4 (\(0^{\circ}\) is considered in forward direction normal to the target position). These spectra are calculated for the pulse duration time, \(5\times 10^{19}\) W/cm\({}^{2}\) laser intensity, and at 3 cm distance from the laser-target  
Figure 4: Simulated spectra of laser accelerated: (**a**) protons; (**b**) electrons beams and (**c**) emitted photons at different angles within 0–15 degrees range. \(0^{\circ}\) is considered in forward direction normal to target. Figure 5: Simulated spectra of laser accelerated: (**a**) electron and (**b**) photon beams at different angles. interaction point. In Figure 4a can be observed, that the most energetic protons are emitted in normal direction to the target position. Within 5 degrees angle the energy of protons drastically decreases. However, the electron spectra presented in Figure 4b indicate only the decrease of electron numbers as the angle increases (see Figure 4b). The spectra of photons also display an angular dependence (see Figure 4c). The spectra obtained for angles between 345\({}^{\circ}\) and 0\({}^{\circ}\) degrees are similar. The interaction between the laser focused spot and target was considered to produce ionizing radiation within 0-360\({}^{\circ}\). The spectra of electrons and photons at different angles between 90\({}^{\circ}\) and 270\({}^{\circ}\) are presented in Figure 5. The number of emitted electrons and photons as well as their energy are lower than those emitted in the 0-15\({}^{\circ}\) range (see Figure 4). Proton spectra were not generated in this angular range. The spectra of electrons, protons, and photons (see Figures 4 and 5) display some fluctuations in the distribution of particles as function of energy. It appears mainly at the highest energies and at angles different from 0\({}^{\circ}\). This is probably due to the statistical approach characteristic to the Monte Carlo simulations [33; 34] and to the fact that the number of generated particles at high energies, is low. Anyway, these fluctuations are relatively small and do not affect the estimations of the electron, proton, and photon spectral distributions.