## 2 Elimaia Diagnostics
### TOF: Description, Test, and Results
Particular care was taken for a proper shielding from the EMP, which typically follows the high power laser-matter interaction and the subsequent plasma production; all the detectorsare provided by an aluminum housing specifically optimized for the EMP shielding with the electronic readout circuit is directly integrated in the detector PCB. These detectors were tested at high power laser facilities in TOF measurements of the high energy laser-driven proton beams generated by the PW Vulcan laser system at the Rutherford Appleton Laboratory (RAL). The experiment was aimed at test diamond detector performances, using TOF technique, with high-energy (up to several tens of MeV) laser-accelerated protons in a laser environment characterized by strong EMP pulse, and compared the results with well-established diagnostics and techniques [21]. A novel analysis method was developed to extract the energy cut-offs, energy distribution, and fluence for energies higher than 10 MeV from the diamond detector TOF signals. The energy distribution and the fluence extracted from the TOF signal were compared with those measured using EBT3 Radiochromic film stacks and TPS coupled with image plate detectors, also allowing one to validate the new data processing method. Data analysis, results, and detailed description of the analysis procedure developed will be presented in following papers. The laser of wavelength of 1.054 um and pulse duration of about 700 fs FWHM delivered up to about 400 J of energy on target in a single shot. The laser was focused on a 25 um Al foil with an incidence angle of 20\({}^{\circ}\) with respect to the target normal by a f/3 off axis parabolic mirror. Figure 4 show pictures of the diamond detectors placed inside the target chamber close to the TPS pinhole (a) and inside a pipe mounted in backward direction (b). As an example of the obtained results, Figure 5 shows a typical TOF signal acquired with the 140 um single diamond detector placed at 2.35 m from the target in the target front-side direction. A 500 um Al foil was used in this shot in front of the diamond detector aperture to stop the most energetic heavy ions accelerated from the target (absorber thickness was chosen based on the TPS spectral analysis) and the low energy proton group. Because of the extreme intense high flux of laser-driven ion bunches, diamond detectors are used in current mode, namely an average current is measured. Figure 4: (a) Picture of the detectors installed in target chamber; (b) Picture of the experimental setup. A TOF signal structure consisiting of a peak arising from UV, X-rays, and fast electrons emitted from the target and a peak generated by the fast proton group can be observed in Figure 5a. Ions other than protons are stopped in the thick Al absorber placed in front of the detector. The short peak appearing at the beginning of time axis (7-12 ns) corresponds to the so-called photo-peak and fixes the starting point for the acquisition, that is, the trigger signal. As one can see in Figure 5a, the low sensitivity of the diamond detector to the plasma visible and soft-UV radiation reflects in a narrow photo-peak compared with other detectors such as Faraday cups and ion collectors, allowing to disentangle the high-energy proton component, characterized by short TOF, also at short flight path as in this case [18; 21]. The Al filter allows selecting a TOF interval in which the signal, being uniquely generated from protons, can be directly converted in energy distribution using the analysis procedure developed for high-energy (up to 100 MeV level) proton spectrum reconstruction, which takes into account the detector response and the proton energy loss inside the detector thickness using a Monte Carlo approach. Figure 5b shows the proton energy distribution extract related to the TOF signal of Figure 5a. Proton energy cut-offs, distribution, and flux were compared with the ones obtained with the RCF stacks and the TPS placed at the same distance and similar angle with respect to the diamond detector.