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This article reports the first measurements of high-energy photons produced with the high-intensity PETawatt Aquitaine Laser (PETAL) laser. The experiments were performed during the commissioning of the laser. The laser had an energy of about 400 J, an intensity of 8 × 1018 W·cm−2, and a pulse duration of 660 fs (FWHM). It was shot at a 2 mm-thick solid tungsten target. The high-energy photons were produced mainly from the bremsstrahlung process for relativistic electrons accelerated inside a plasma generated on the front side of the target. This paper reports measurements of electrons, protons and photons. Hot electrons up to ≈35 MeV with a few-MeV temperature were recorded by a spectrometer, called SESAME (Spectre ÉlectronS Angulaire Moyenne Énergie). K- and L-shells were clearly detected by a photon spectrometer called SPECTIX (Spectromètre Petal à Cristal en TransmIssion pour le rayonnnement X). High-energy photons were diagnosed by CRACC-X (Cassette de RAdiographie Centre Chambre-rayonnement X), a bremsstrahlung cannon. Bremsstrahlung cannon analysis is strongly dependent on the hypothesis adopted for the spectral shape. Different shapes can exhibit similar reproductions of the experimental data. To eliminate dependence on the shape hypothesis and to facilitate analysis of the data, simulations of the interaction were performed. To model the mechanisms involved, a simulation chain including hydrodynamic, particle-in-cell, and Monte Carlo simulations was used. The simulations model the preplasma generated at the front of the target by the PETAL laser prepulse, the acceleration of electrons inside the plasma, the generation of MeV-range photons from these electrons, and the response of the detector impacted by the energetic photon beam. All this work enabled reproduction of the experimental data. The high-energy photons produced have a large emission angle and an exponential distribution shape. In addition to the analysis of the photon spectra, positron production was also investigated. Indeed, if high-energy photons are generated inside the solid target, some positron/electron pairs may be produced by the Bethe–Heitler process. Therefore, the positron production achievable within the PETAL laser facility was quantified. To conclude the study, the possibility of creating electron/positron pairs through the linear Breit–Wheeler process with PETAL was investigated.

The discovery of chirped pulse amplification has led to great improvements in laser technology, enabling energetic laser beams to be compressed to pulse durations of tens of femtoseconds and focused to a few micrometers. Protons with energies of tens of MeV can be accelerated using, for instance, target normal sheath acceleration and focused on secondary targets. Under such conditions, nuclear reactions can occur, with the production of radioisotopes suitable for medical application. The use of high-repetition lasers to produce such isotopes is competitive with conventional methods mostly based on accelerators. In this paper, we study the production of 67Cu, 63Zn, 18F, and 11C, which are currently used in positron emission tomography and other applications. At the same time, we study the reactions 10B(p,α)7Be and 70Zn(p,4n)67Ga to put further constraints on the proton distributions at different angles, as well as the reaction 11B(p,α)8Be relevant for energy production. The experiment was performed at the 1 PW laser facility at Vega III in Salamanca, Spain. Angular distributions of radioisotopes in the forward (with respect to the laser direction) and backward directions were measured using a high purity germanium detector. Our results are in reasonable agreement with numerical estimates obtained following the approach of Kimura and Bonasera [Nucl. Instrum. Methods Phys. Res., Sect. A 637, 164–170 (2011)].

The high-energy petawatt PETAL laser system was commissioned at CEA’s Laser Mégajoule facility during the 2017–2018 period. This paper reports in detail on the first experimental results obtained at PETAL on energetic particle and photon generation from solid foil targets, with special emphasis on proton acceleration. Despite a moderately relativistic (

Quasi-static magnetic-fields up to 800 T are generated in the interaction of intense laser pulses (500 J, 1 ns, ${10}^{17}\;{\rm{W}}\;{\mathrm{cm}}^{-2}$ ) with capacitor-coil targets of different materials. The reproducible magnetic-field peak and rise-time, consistent with the laser pulse duration, were accurately inferred from measurements with GHz-bandwidth inductor pickup coils (B-dot probes). Results from Faraday rotation of polarized optical laser light and deflectometry of energetic proton beams are consistent with the B-dot probe measurements at the early stages of the target charging, up to $t\approx 0.35$ ns, and then are disturbed by radiation and plasma effects. The field has a dipole-like distribution over a characteristic volume of 1 mm ^3 , which is consistent with theoretical expectations. These results demonstrate a very efficient conversion of the laser energy into magnetic fields, thus establishing a robust laser-driven platform for reproducible, well characterized, generation of quasi-static magnetic fields at the kT-level, as well as for magnetization and accurate probing of high-energy-density samples driven by secondary powerful laser or particle beams.