Fabricated Germanium Doped Optical Fibres (FGDOF) for Electron Beams Dosimetry

Abstract

A new dosimeter, namely, Fabricated Germanium Doped Optical Fibres (FGDOF) is developed for electron beam dosimetry. The objectives were investigated the basic and advanced dosimetric characteristics of FGDOF in electron beam dosimetry. Two types of FGDOF, cylindrical fibre (CF) and flat fibre (FF) were doped with 2.3 and 6 mol% germanium. Electron beam energies from 6 MeV to 12 MeV, doses from 1 Gy to 5 Gy, dose rates from 100 to 600 cGy/min, focus to surface distance of 100 cm, and various field sizes were employed to analyse the FGDOF dosimetric capabilities. Comparisons were made with commercial fibres, Lithium Fluoride (LiF) chips, GafchromicTM EBT3 films (EBT3 films), and ionisation chamber (IC). For reproducibility, both CF and FF had a coefficient of variation of less than 5%. FGDOF demonstrated a linear thermoluminescence (TL) response across the examined doses and energies. In terms of sensitivity, FF had a higher sensitivity by a factor of two compared to CF. The minimum detectable dose (MDD) calculated has shown that FGDOF is good at low-dose detection. Insignificant differences (p > 0.05) were found for FGDOF with a percentage difference within ± 5% in terms of field size and dose-rate dependence. Conversely, FGDOF showed energy dependency with a p ≤ 0.05 (95% confidence level). 23FF showed the lowest signal fading loss between 4.1 % and 5.9 % for a storage period of 13 days. Percentage depth dose (PDD) of FGDOF in a solid waterTM phantom is within 5% and agreeable to IC with no notable variations found in the build-up and fall-off regions. FGDOF also presented no discrepancies over the electron energies regarding the output factor. In conclusion, the developed FGDOF, particularly FF was found to be suitable for electron beam dosimetry.