Abstract
Optically transparent LiF thin films thermally evaporated on glass and Si(100) substrates were used for advanced diagnostics of proton beams of energies from 1.4 to 7 MeV produced by a linear accelerator for protontheraphy under development at ENEA C.R. Frascati. The proton irradiation induces the formation of stable colour centres, among them the aggregate F2 and F3+ optically active defects. After exposure of LiF films grown on glass perpendicularly to the proton beams, their accumulated transversal spatial distributions were carefully measured by reading the latent two-dimensional (2-D) fluorescence images stored in the LiF thin layers by local formation of these broad-band visible light-emitting defects with an optical microscope under blue lamp excitation. Taking advantage from the low thickness of LiF thin films and from the linear behaviour of the integrated F2 and F3+ photoluminescence intensities up to the irradiation fluence of ∼5x1015 p/cm2, placing a cleaved LiF film grown on Si substrate with the cutted edge perpendicular to the proton beam, the 2-D fluorescence image of the film surface could allow to obtain the depth profile of the energy released by protons, which mainly lose their energy at the end of the path.
Highlights
Luminescence properties of point defects in insulating materials are successfully used for solid state light sources and dosimeters
After exposure of LiF films grown on glass substrates perpendicularly to the proton beams, their accumulated transversal spatial distributions were measured by reading with a conventional optical microscope the latent two-dimensional (2-D) fluorescence images stored in the LiF thin layers by local formation of optically active colour centres (CCs) at irradiation fluence in the range 1011-1015 p/cm2 [5,6]
Placing a cleaved LiF film grown on a Si(100) substrate [8] with the cut edge perpendicular to the proton beam direction, so that the film surface is parallel to the direction of the impinging particles, the 2-D fluorescence images could allow to obtain the depth profile of the energy released by protons, which mainly lose their energy at the end of the path [10,11]
Summary
Luminescence properties of point defects in insulating materials are successfully used for solid state light sources and dosimeters. Broad-band light-emitting F2 and F3+ colour centres (CCs) in lithium fluoride, LiF, are well known for their application in tuneable lasers, miniaturised light sources and radiation imaging detectors [1]. The F2 and F3+ laser-active CCs in LiF possess almost overlapping absorption bands peaked around 450 nm, called M band [3]; under light excitation in this spectral range they emit broad PL bands peaked at 678 nm and 541 nm, respectively [4], whose intensities can be detected by an optical microscope operating in fluorescence mode. Among the main peculiarities of the luminescent LiF-film solid-state radiation imaging detectors, noteworthy ones are their very high intrinsic spatial resolution, and wide dynamic range. Due to the stability of F2 and F3+ CCs at room temperature (RT) in LiF, they are quite easy to handle, as insensitive to ambient light
Sign-in/Register to view highlights & summary 
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: IOP Conference Series: Materials Science and Engineering
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
