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 7 MeV energy, in a fluence range from 10 11 to 10 15 protons/cm 2 . In the LiF films, proton irradiation induces the formation of F2 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.

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We report the first experiment aimed at the demonstration of low-energy protons acceleration by a high-efficiency S-band RF linear accelerator. The proton beam has been accelerated from 7 to 11.6 MeV by a 1 meter long SCDTL (Side Coupled Drift Tube Linac) module powered with 1.3 MW. The experiment has been done in the framework of the Italian TOP-IMPLART (Oncological Therapy with Protons-Intensity Modulated Proton Therapy Linear Accelerator for Radio-Therapy) project devoted to the realization of a proton therapy centre based on a proton linear accelerator for intensity modulated cancer treatments to be installed at IRE-IFO, the largest oncological hospital in Rome. It is the first proton therapy facility employing a full linear accelerator scheme based on high-frequency technology.

Systematic irradiation of thermally evaporated 0.8 μm thick polycrystalline lithium fluoride films on glass was performed by proton beams of 3 and 7 MeV energies, produced by a linear accelerator, in a fluence range from 1011 to 1015 protons/cm2. The visible photoluminescence spectra of radiation-induced F2 and F3+ laser active color centers, which possess almost overlapping absorption bands at about 450 nm, were measured under laser pumping at 458 nm. On the basis of simulations of the linear energy transfer with proton penetration depth in LiF, it was possible to obtain the behavior of the measured integrated photoluminescence intensity of proton irradiated LiF films as a function of the deposited dose. The photoluminescence signal is linearly dependent on the deposited dose in the interval from 103 to about 106 Gy, independently from the used proton energies. This behavior is very encouraging for the development of advanced solid state radiation detectors based on optically transparent LiF thin films for proton beam diagnostics and two-dimensional dose mapping.