Silica based fibres for radiation dosimetry
Creators: name: TERMSUK, CHUTIMA
Publisher: name: University of Surrey
Year: 2022

description: "This thesis reports the potential of commercial silica based fibres with different Ge doped core
description: concentrations for radiation dosimetry. Fibre samples studied included multi-mode 4 and 6%Ge
description: doped core purchased from CorActive, Canada, single-mode 17%Ge 1%B (GeB) and undoped
description: coreless silica fi bres supported by Fibercore, UK. Scanning Electron Microscope (SEM) and Energy
description: Dispersive x-ray Spectroscopy (EDS) measured the effective atomic number of these fi bres
description: between 14 and 18 which is similar to human bone, the chemical composition was con firmed to
description: be uniform across the fi bre cross-section. In a fi ve millimeter fi bre length thermoluminescence
description: study, the undoped silica fi bre had no thermoluminescence (TL) response. The 6% Ge doped fibre
description: showed the best sensitivity with and without core size correction, 15082±687 counts•mm-1•Gy-1
description: and 7.69±0.35 counts•mm-1•Gy-1•µm-2 respectively. This fi bre also represented an optimal
description: concentration; over this amount dopant contributed to the self-absorption of luminescence.
description: The TL glow curve from Ge doped fibre exhibited a broad peak shape extending beyond
description: 400 °C. When increasing Ge dopant from 4 up to 17 %, the main peak temperature, TM was shifted
description: to lower temperature; from 317±2 to 249±3 °C. This result suggests that different dosimetry
description: readout temperature settings should be applied for different percentage doped Ge fibre. This fi nding
description: also bene fits new TL material development, with the advantage of lower readout temperature.
description: TolAnal CGCD software and peak fi tting function in MATLAB revealed that overlapping of fi ve
description: sub-peaks caused the broad peak shape. This software was also consistent with the Chen peak
description: shape method in that the electron trap energies ranged from 0.5 to 1.5 eV. This helps consider
description: the sufficient activation energy to create recombination leading to luminescence. For medical
description: applications the results indicate using a 6%Ge fibre readout at 302 °C.
description: OpticalStudio (Zemax) ray tracing software was applied to study TL propagation in 4%
description: Ge doped fi bre. Where the luminescence originates in core volume, 68±5% of luminescence is
description: emitted around the fi bre side. This supports that TL readout from fi ve millimeter fi bre dosimeter,
description: by facing the long dimension of the fi bre towards the photomultiplier (PMT), can maximise the
description: collected TL signal. The 27±5% of luminescence exited from the combined fibre ends provides an
description: opportunity to measure signal from fibre ends when the long length fi bre (metres) is used. In
description: Optically Stimulated Luminescence (OSL) investigation, two metres of 4 and 6%Ge doped fibres
description: were tested with two laser wavelengths; 1540 and 532 nm. As high attenuation induced by radiation
description: took place on the whole fibre length, the laser intensity was reduced, contributing to the absence
description: of the OSL signal. The TL glow curve study after laser treatment exhibited that the energy from
description: 532 eV is sufficient to release trapped electrons."