Proton beam dose-mapping via color centers in LiF thin-film detectors by fluorescence microscopy

With the purpose of studying the behavior of novel solid-state lithium fluoride (LiF) films detectors based on the photoluminescence (PL) of radiation-induced defects for proton beam diagnostics and dosimetry, polycrystalline LiF thin films thermally evaporated on glass were irradiated at room temperature in a linear proton accelerator under development at ENEA. The irradiations were performed in air by proton beams of 3 and 7MeV energy, in a fluence range from 10(11) to 10(15) protons/cm(2). In the LiF films, proton irradiation induces the formation of F-2 and F-3(+) aggregate color centers, which simultaneously emit broad PL bands in the visible spectral range under excitation in the blue one. The integrated PL signal, acquired by a fluorescence microscope equipped with a s-CMOS camera, shows a linear dependence on the dose deposited in LiF films, extending from 10(3) to 10(6) Gy, independently of the proton energy. A simple theoretical model is put forward for the formation of color centers in LiF and is utilized to obtain a proton beam dose-map by processing the PL image stored in the LiF film detectors. Copyright (C) EPLA, 2017