Proton spectroscopy for 11B(p,α)2α fusion reaction with RCF films: calibration and unfolding procedure

The reaction occurring between protons and 11B isotope (p+11B → 3α+8.7 MeV) has recently attracted attention as a possible candidate to overcome the generation of high-energy neutrons via the more studied Deuterium-Tritium fusion reaction. Since the early 2000s, several experiments have been carried out to investigate the viability of triggering this aneutronic reaction in laser-target interaction schemes. During these experiments, the total number of escaping α particles is measured to infer fusion reaction efficiency. However, the accurate detection of α particles in such experiments poses a real challenge. In this scenario, RadioChromic Films (RCFs) arranged in a stack configuration can be used for the fluence and energy spectra reconstruction of generated protons, being this mandatory information in both “pitcher-catcher” and “in plasma” p-11B irradiation schemes. Nevertheless, RCF response exhibits a dependence on Linear Energy Transfer (LET), which leads to an underestimation of the response in high-LET conditions. This can result in dosimetric errors if not properly taken into account. In this work, an analytical procedure able to reconstruct the incident energy spectra in an RCF stack was developed and validated thanks to a calibration procedure that was established for high and low proton energy (4–60 MeV) beams to properly reconstruct the incident spectra in the “pitcher-catcher” irradiation scheme.