Hashim, S and Al-Ahbabi, S and Bradley, D.A. and Webb, M and Jeynes, C and Ramli, Ahmad Termizi and Wagiran, H The thermoluminescence response of doped SiO2 optical fibres subjected to photon and electron irradiations. Applied Radiation and Isotopes . (In Press)
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Official URL: http://dx.doi.org/10.1016/j.apradiso.2008.06.030
Modern linear accelerators, the predominant teletherapy machine in major radiotherapy centres worldwide, provide multiple electron and photon beam energies. To obtain reasonable treatment times, intense electron beam currents are achievable. In association with this capability, there is considerable demand to validate patient dose using systems of dosimetry offering characteristics that include good spatial resolution, high precision and accuracy. Present interest is in the thermoluminescence response and dosimetric utility of commercially available doped optical fibres. The important parameter for obtaining the highest TL yield during this study is to know the dopant concentration of the SiO2 fibre because during the production of the optical fibres, the dopants tend to diffuse. To achieve this aim, proton-induced X-ray emission (PIXE), which has no depth resolution but can unambiguously identify elements and analyse for trace elements with detection limits approaching Î¼g/g, was used. For Al-doped fibres, the dopant concentration in the range 0.98-2.93 mol% have been estimated, with equivalent range for Ge-doped fibres being 0.53-0.71 mol%. In making central-axis irradiation measurements a solid waterâ„¢ phantom was used. For 6-MV photons and electron energies in the range 6, 9 and 12 MeV, a source to surface distance of 100 cm was used, with a dose rate of 400 cGy/min for photons and electrons. The TL measurements show a linear dose-response over the delivered range of absorbed dose from 1 to 4 Gy. Fading was found to be minimal, less than 10% over five days subsequent to irradiation. The minimum detectable dose for 6-MV photons was found to be 4, 30 and 900 Î¼Gy for TLD-100 chips, Ge- and Al-doped fibres, respectively. For 6-, 9- and 12-MeV electron energies, the minimum detectable dose were in the range 3-5, 30-50 and 800-1400 Î¼Gy for TLD-100 chip, Ge-doped and Al-doped fibres, respectively.
|Uncontrolled Keywords:||Dopants, PIXE and RBS analysis, SiO2 optical fibres, thermoluminescence|
|Subjects:||Q Science > QC Physics|
|Deposited By:||Maznira Sylvia Azra Mansor|
|Deposited On:||09 Jan 2009 07:03|
|Last Modified:||09 Jan 2009 08:39|
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