Spectral characterization of 63 and 71 MeV proton beams using localized random search fitting of radiophotoluminescent Bragg curves in lithium fluoride crystals

When a proton beam irradiates lithium fluoride, stable point defects—known as color centers—are formed within the material, some of which are laser-active. The volumetric concentration of these defects depends on the energy spectrum of the incident protons. By detecting and analyzing the spatial distribution of their visible radiophotoluminescence, it is possible to quantitatively reconstruct the shape of the proton energy spectrum. In this work, a localized random search optimization method is applied to proton energies in the tens-of-MeV range, using a previously developed analytical model of Bragg curves in LiF. The model includes an empirical correction, introduced in earlier work, to account for proton leakage due to multiple Coulomb scattering. The method is validated through two case studies involving nominal proton beam energies of 63 and 71 MeV at the TOP-IMPLART linear accelerator facility. • LiF photoluminescent crystals for the energy diagnostics of proton beams. • Creation of color centers in a LiF crystal by proton irradiation. • Proton-beam energy spectrum estimation from photoluminescent Bragg curves. • Bragg-curve fitting via localized random search of energy spectrum bin heights. • TOP-IMPLART linear accelerator high-energy beam spectral characterization.