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High-power pulsed lasers are used more and more as tools for particle acceleration. Characterization of the accelerated particles in real-time and monitoring of the electromagnetic pulses (EMPs) during particle acceleration are critical challenges in laser acceleration experiments. Here, we used the CETAL-PW laser facility at NILPRP for particle acceleration from different thin metallic targets, at laser intensities of the order of 3×1021 W/cm2. We investigated the dependence of EMP amplitude (EMPA) and the accelerated electrons’ maximal energy (AEME), on thickness, resistivity, and atomic number of the target. We have found a quasi-linear dependence between EMPA and AEME and propose an analytical model for the GHz EMP emission. The model considers the neutralization current flowing through the target stalk as the main source of the EMP in the GHz domain, the current being produced by the positive charge accumulated on the target after the electron’s acceleration from the rear side of a metallic target. The data presented here support the possibility of using EMP signals to characterize the laser-accelerated particles in a real-time non-invasive way.

An adequate simulation model has been used for the calculation of angular and energy distributions of electrons, protons, and photons emitted during a high-power laser, 5-µm thick Ag target interaction. Their energy spectra and fluencies have been calculated between 0 and 360 degrees around the interaction point with a step angle of five degrees. Thus, the contribution of each ionizing species to the total fluency value has been established. Considering the geometry of the experimental set-up, a map of the radiation dose inside the target vacuum chamber has been simulated, using the Geant4 General Particle Source code, and further compared with the experimental one. Maximum values of the measured dose of the order of tens of mGy per laser shot have been obtained in the direction normal to the target at about 30 cm from the interaction point.

We show that a spectral distribution of laser-accelerated protons can be extracted by analyzing the proton track diameters observed on the front side of a second CR-39 detector arranged in a stack. The correspondence between the proton track diameter and the incident energy on the second detector is established by knowing that protons with energies only higher than 10.5 MeV can fully deposit their energy in the second CR-39 detector. The correlation between the laser-accelerated proton track diameters observed on the front side of the second CR-39 detector and the proton incident energy on the detector stack is also presented. By calculating the proton number stopped in the CR-39 stack, we find out that its dependence on the proton energy in the 1−15 MeV range presents some discontinuities at energies higher than 9 MeV. Thus, we build a calibration curve of the track diameter as a function of the proton incident energy within the 1−9 MeV range, and we infer the associated analytical function as the calculations performed indicate best results for proton spectra within the 1−9 MeV range. The calibration curve is used as a tool to ascertain the pits identified on the surfaces of both CR-39 detectors to proton tracks. The proton tracks spatial distribution analyzed by optical and atomic force microscopy is correlated with the peculiarity of the used targets.