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• Photoluminescence behavior of color centers in LiF irradiated by 18 MeV protons. • Proton beam imaging by visible photoluminescence of color centers in LiF crystals. • Photoluminescence saturation dose from Bragg curve profiles reconstruction. • Photoluminescence saturation dose from proton beam transversal intensity maps. • Reliable method for proton-beam diagnostics and LiF dose response investigation. The paper concerns the analysis of spatial distributions of visible photoluminescence of optically active F 2 and F 3 + color centers created in lithium fluoride crystals by irradiation with proton beams. Spectrally integrated photoluminescent maps are detected in a fluorescence microscope and numerically elaborated to gather pieces of information regarding both the beam characteristics and the material response. A method based on two independent measurements (Bragg curve and beam transversal map) is developed to evaluate the saturation dose defined as the value above which the photoluminescence intensity begins saturating up to an asymptotic maximum. The paper describes the procedure and demonstrates its application to the experimental case of LiF crystals irradiated by a proton beam of 18 MeV nominal energy. [ABSTRACT FROM AUTHOR]

Abstract: Lithium fluoride is a well-known dosimeter material and it is currently under investigation also for high-resolution radiation imaging detectors based on colour centre photoluminescence. In order to extend their applications, proton beams of 3MeV energy, produced by a linear accelerator, were used to irradiate LiF crystals and thin films in the fluence range of 1010–1015 protons/cm2. The irradiation induces the formation of colour centres, mainly the primary F centre and the aggregate F2 and defects, which are stable at room temperature. By optical pumping in the blue spectral region, the F2 and centres emit broad photoluminescence bands in the visible spectral range. By conventional fluorescence microscopy, the integrated photoluminescence intensity was carefully measured in LiF crystals and thin films as a function of the irradiation fluence: a linear optical response was obtained in a large range of fluence, which is dependent on the used LiF samples. Colour centres concentrations were estimated in LiF crystals by optical absorption spectroscopy. It was possible to record the transversal proton beam intensity profile by acquiring the photoluminescence image of the irradiated spots on LiF films. [Copyright &y& Elsevier]

Abstract: We report about the light-emitting properties of colour centres in lithium fluoride thin films and crystals treated with low-penetrating extreme-ultraviolet radiation and soft X-rays. Experimental fluorescence-imaging results show that, under the same irradiation conditions, stronger photoluminescence, up to a factor eight, is released by colour centres in a film thermally grown on silicon substrate than in a crystal. By using a classical-electromagnetism model, we take into account the role of the silicon substrate in the enhancement of spontaneous emission over a broad spectral range to analyze such behaviour. [ABSTRACT FROM AUTHOR]