Schematic experimental arrangement for proton-induced reactions. The ultraintense laser beam was focused on the primary target to generate tens of MeV protons, which reacted with the samples in front of and behind the target.
Regions of characteristic -ray line spectra for the proton-irradiated zinc samples, measured with germanium detectors. Typical lines for the nuclei have been labeled in the spectra.
Proton energy spectra measured at the front and back of a -thick aluminium target foil irradiated with a laser pulse. The spectra were deduced from observed proton-induced reactions in zinc samples and are in good agreement with proton energy spectra measured with other VULCAN petawatt laser shots and using nuclear activation of Cu foil stacks (see Refs. 9 and 20). The total conversion efficiency from laser-pulse energy to proton acceleration (in both directions) is . This was calculated by integrating the spectrum in the figure to determine the total energy in the ion beam and dividing this by the energy in the laser shot. The 13% value is typical for large, high-energy pulse laser (see Ref. 4).
Numbers of neutrons produced by reactions in the front and back boron samples as function of the target thicknesses.
Cross sections for the reactions in , , , , , , and samples (see Ref. 28).
Calculated numbers of neutrons generated by reactions in the , , , , , , and samples as a function of their thickness for (a) front samples and (b) back samples.
Calculated neutron energy spectra generated in the forward direction of the proton beams by reactions in , , , and samples.
Residual nuclei observed in the zinc activation target and corresponding proton-induced reactions.
Observed number of nuclear produced via nuclear reactions induced by proton beams from the front and back of the different laser-irradiated targets.
Calculated maximum numbers of neutrons per steradian produced by reactions in activation samples.
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