Fig. 1. (a) Schematic of the equatorial layout of the experimental setup with the positions of the diagnostics indicated. (b) SPECTIX: hard-X ray spectrometer. (c) CRACC-X: bremsstrahlung spectrometer. (d) SESAME 1 and 2: electron and ion spectrometers.

Fig. 2. SESAME electron energy spectra obtained at 0° (blue curves) and 45° (red curves) for (a) shot SR174 and (b) shot SR182. The exponential fit (∼Ae^−E/T) of each spectrum is also given (black curves).

Fig. 3. SESAME proton energy spectra obtained at 0° (blue curves) and 45° (red curves) for (a) shot SR174 and (b) shot SR182.

Fig. 4. Absolute temporally and spatially integrated X-ray spectra measured by SPECTIX for (a) shot SR174 with a LiF(200) crystal and (b) shot SR182 with a quartz (10-10) crystal (red curve) and a LiF(200) crystal (blue curve). Black vertical lines represent the exact energy of each emission line of tungsten. The inserts in (b) are zooms on zones of interest of the spectra.

Fig. 5. CRACC-X sensitivity response for each IP, inferred from GEANT4 simulations.

Fig. 6. Diagram of simulation chain setup used to calculate high-energy photon emission.

Fig. 7. Lineouts of the electron density profile of the preplasma for aluminum + plastic (orange) and tungsten (blue) targets from 2D axisymmetric TROLL simulations. The lineouts are taken at 1 μm from the central axis of the laser. The green curves correspond to a translation of the aluminum profile to superimpose the tungsten and the aluminum at 1n_c. The red dashed lines correspond to the limits of the density profile used for the PIC simulations, which goes from 10n_c to 0.1n_c.

Fig. 8. Initial electron spectrum (red) from a 2D PIC CALDER simulation on a multilayer of Al (150 μm) followed by CH (10 μm) at 1.5 ps with a total a₀ of 2.4 and the electron energy distribution generated at low energies (purple) with a temperature of 0.6 MeV. The blue line corresponds to the cutoff at 4 MeV. For the PIC target parameter, the aluminum density was taken from the hydrodynamic simulation, and the CH initially had a density of 20n_c.

Fig. 9. Photon spectrum obtained with Geant4 (red) at the rear side of the tungsten target of 2 mm thickness and (blue) photon spectrum interacting with the detector generated by the interaction with an electron beam of energy 253 J. The inset is a zoom of the low-energy part of the photon spectrum in red.

Fig. 10. Spectra of all electrons at the rear side of the target (blue) and of those electrons that interact with the CRACC-X detector (green).

Fig. 11. Comparison between the measured spectra (dots) and the simulated data (curves) for an initial total electron energy of 253 J for SESAME 1 (blue) and SESAME 2 (red).

Fig. 12. (a) Energy deposition in each IP of the CRACC-X detector measured in the experiment (blue dots) and calculated using the simulation chain, with the contributions of the simulated populations of photons (green), electrons (red), and the sum of the two contributions (orange). These results are for an initial total electron energy of 253 J. (b) Energy deposited in each IP for different initial total electron energies.

Fig. 13. Positron energy spectrum at the rear side of the tungsten target at the end of the simulation. The electron initial total energy for the positron production is 253 J and the target is 2 mm thick.

Fig. 14. Number of positrons obtained in the Geant4 simulations normalized by the electron beam initial energy as a function of the Y parameter with electron/positron annihilation activated (blue) and without activation (red). The electron beam has an initial total energy of 253 J, and it interacts with tungsten targets of different thicknesses.

Fig. 15. Schematic of proposed configuration to produce Breit–Wheeler positrons with the PETAL facility.

Fig. 16. Number of LBW positrons produced by the collision of two γ beams colliding at an angle of 135° and a distance L = 0.05 cm, vs tungsten thickness. The electron initial total energy considered for the beam generation is 253 J.

Fig. 17. (a) Breit–Wheeler positron energy spectrum and (b) angular distribution produced by the collision of two γ beams, colliding at an angle of 135° and a distance L of 0.05 cm, and produced by an electron initial total energy of 253 J with a 0.8 mm tungsten target tickness.

Table 1. Laser parameters for the two shots on tungsten targets.

Table 2. Properties of K-shell emission lines detected with the SPECTIX diagnostic.

Table 3. Composition of the CRACC-X diagnostic. An IP is placed downstream of each filter.

Table 4. Rear-side atomic lines for a cold tungsten target obtained by the Geant4 simulation.

Table 5. Front-side atomic lines for a cold tungsten target obtained by the Geant4 simulation (Sim.) and K-shell emission lines detected with the SPECTIX diagnostic for shot SR174 (Expt.) from Table II.