Fig. 1. (a) Top view of experimental setup. The laser impinges on the Al “pitcher” target (6 μm thickness) at a 12° angle. Ion and electron diagnostics are shown, together with the Al shield. (b) Zoomed view of the pitcher–catcher configuration and the CR39 detector array (note that the pictured distances, dimensions, and angles are not in scale with each other). The horizontal width of P1 + P2 + P3 is 100 mm.

Fig. 2. Typical spectra of protons (blue) and carbon ions (orange) measured at the Al target normal. The spectra were obtained by averaging the data from 31 shots (protons) and 19 shots (carbon ions) and are here averaged to a single shot; the error bars indicate one standard deviation. The dashed lines indicate Maxwell–Boltzmann fits for protons (red and green) and carbon ions (black).

Fig. 3. (a) Electron spectra measured on the Al target rear side (top plot) and front side (bottom plot). Both spectrometers were placed on the target equatorial plane. The spectra were obtained by averaging over 123 laser shots and are here averaged to a single shot. (b) Electron spectrum from the front side of the Al target, fitted with two Maxwell–Juttner functions, for the cold and hot components of the laser-accelerated electrons. The obtained temperatures are 0.511 (red) and 3.125 MeV (green).

Fig. 4. (a) Spectrum, averaged over 71 shots, of TNSA protons backscattered from the B catcher. (b) Microscope image (broad and zoomed view) of the trace (associated with protons) obtained on the CR39.

Fig. 5. On the left is shown one of the implemented CR39s, divided into four regions with different filter types, while the complete scheme of the implemented filters is shown on the right.

Fig. 6. Calibration curves of CR39 detectors for protons and alpha particles. The reported dimensions of the traces left by the particles are for (a) 60, (b) 90, and (c) 120 min of etching. The horizontal red dashed lines indicate the calibration range where the track dimension is unequivocal, i.e., cannot be attributed to protons. The vertical black dashed lines indicate the corresponding energy window.

Fig. 7. Density of traces as a function of their areal dimensions revealed by the CR39 at position P3. The plots are for the regions with (a) a 2 μm PET filter, (b) a 6 μm Al filter, and (c) a 10 μm Al filter. The blue part of the curves indicates traces which cannot be attributed unequivocally to a specific ion species, i.e., they are generated by protons and/or heavy ions. The red part of the curves indicates the range where the trace dimension allows protons to be discriminated on the basis of the calibrations of Fig. 6. These are indicated in the legend as potential alpha particles, provided no heavier ions are impinging on the CR39.

Fig. 8. (a) Spectra of scattered protons (green), scattered C ions (brown), in the case of equal atomic mass in the catcher, and alpha particles that reach the position of the CR39 detector (red). In this case, no filter is considered, i.e., the spectra are calculated considering the particles as they are scattered/generated at the B catcher. As reference, the measured spectra of TNSA protons (blue) and C ions (orange) are also added from Fig. 2. The purple curve represents the measured scattered protons of Fig. 4(a). (b) Spectra of scattered protons (green), scattered C ions (brown), and alpha particles that pass through the filters that were used in the CR39 experimental configurations (red).

Fig. 9. Estimated alpha particle spectrum detected by the CR39 array. The black dots were obtained with an etching time of 90 min, for a 43-shot series. The green dots were obtained with a 60 min etching time for a 46-shot series. The red curve represents the analytical spectrum of expected alpha particles that impinge on the detector.

Fig. 10. (a) Microscope image of the irradiated B sample after multiple-shot irradiation. The “marked” areas indicate the presence of Al debris on the irradiated surface and can serve as an indication on the correct alignment of the catcher with respect to the pitcher. (b) Lineouts (horizontal at the top and vertical at the bottom) of the gray values of the microscope image [indicated on the image in (a) by the red dashed lines].

Fig. 11. CR39 microscope images from the pitcher–catcher setup, with and without an Al shield protecting the detector array. The upper image is in the absence of the protecting Al screen, after a series of 86 shots, without the B catcher. The lower image is of a CR39 at the same position, after a series of 20 shots without the catcher, but with the protecting Al screen in place.