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You searched for subject:(Fluorophosphate glass). Showing records 1 – 3 of 3 total matches.

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1. Vahedi, Shahrzad. Optical and thermal properties of samarium-doped fluorophosphate and fluoroaluminate glasses for high-dose, high-resolution dosimetry applications.

Degree: 2014, University of Saskatchewan

Microbeam radiation therapy (MRT) is an experimental form of radiation treatment which causes less damage to normal tissue in comparison with customary broad-beam radiation treatment. In this method the synchrotron generated X-ray beam is passed through a multislit collimator and applied to the tumor in the form of an array of planar microbeams. MRT dosimetry is an extremely challenging task and no current detector can provide the required wide dynamic rang and high spatial resolution. In this thesis, fluorophosphate (FP) and fluoroaluminate (FA) glass plates doped with trivalent samarium (Sm3+) are characterized towards developing a potential X-ray detector suitable for MRT dosimetry. The detection is based on the difference in the photoluminescence signatures of Sm3+ ions and Sm2+ ions; the latter are formed under X-ray irradiation. This valency conversion is accompanied by the formation of defects including hole centers (HCs) and electron centers (ECs) in the glass structure which absorb light in the UV and visible regions (induced absorbance). Both FP and FA glasses show promising dynamic range for MRT and may be used as a linear sensor up to ~150 Gy and as a nonlinear sensor up to ∼2400 Gy, where saturation is reached. X-ray induced defects saturate at the same dose. The optimum doping concentration is in the 0.001˗ 0.2 at.% range. Doping with higher concentrations will decrease the conversion efficiency. The glass plates also show a very promising spatial resolution (as high as a few microns) for recording the dose profile of microbeams which is readout using a confocal fluorescence microscopy technique. These plates are restorable as well and the response is reproducible. The effects of previous X-ray exposure including samarium valency conversion as well as induced absorbance may be erased by annealing at temperatures exceeding the glass transition temperature Tg while annealing at TA < Tg enhances the response. This enhancement is explained by a thermally stimulated relaxation of host glass ionic matrix surrounding X-ray induced Sm2+ ions. Optical erasure is another practical means to erase the recorded data. Nearly complete Sm2+ to Sm3+ reconversion (erasure) is achieved by intense optical illumination at 405 nm. While, existing X-ray induced bands would be only partially erased. Electron spin resonance (ESR) and optical absorbance spectroscopy are used to investigate the nature of X-ray induced defects and their correlation with Sm valency conversion. A model based on competition between defect center formation and the Sm3+ ⇆ Sm2+ conversion successfully explains the different processes occurring in the glass matrix under X-ray irradiation. Advisors/Committee Members: Kasap, Safa, Chapman, Dean, Chen, Li, Zhang, Chris, Bui, Francis, Yang, Qiaoqin.

Subjects/Keywords: Samarium-doped glass; Fluorophosphate glass; Fluoroaluminate glass; Valency conversion; Dosimetry; Microbeam radiation therapy (MRT); X-ray induced defects

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Vahedi, S. (2014). Optical and thermal properties of samarium-doped fluorophosphate and fluoroaluminate glasses for high-dose, high-resolution dosimetry applications. (Thesis). University of Saskatchewan. Retrieved from http://hdl.handle.net/10388/ETD-2014-10-1780

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Vahedi, Shahrzad. “Optical and thermal properties of samarium-doped fluorophosphate and fluoroaluminate glasses for high-dose, high-resolution dosimetry applications.” 2014. Thesis, University of Saskatchewan. Accessed October 20, 2019. http://hdl.handle.net/10388/ETD-2014-10-1780.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Vahedi, Shahrzad. “Optical and thermal properties of samarium-doped fluorophosphate and fluoroaluminate glasses for high-dose, high-resolution dosimetry applications.” 2014. Web. 20 Oct 2019.

Vancouver:

Vahedi S. Optical and thermal properties of samarium-doped fluorophosphate and fluoroaluminate glasses for high-dose, high-resolution dosimetry applications. [Internet] [Thesis]. University of Saskatchewan; 2014. [cited 2019 Oct 20]. Available from: http://hdl.handle.net/10388/ETD-2014-10-1780.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Vahedi S. Optical and thermal properties of samarium-doped fluorophosphate and fluoroaluminate glasses for high-dose, high-resolution dosimetry applications. [Thesis]. University of Saskatchewan; 2014. Available from: http://hdl.handle.net/10388/ETD-2014-10-1780

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

2. Silva, Raphaell Júnnio Moreira. Caracterização estrutural de vidros fluorofosfatos utilizando metodologias de RMN.

Degree: Mestrado, Física Aplicada, 2014, University of São Paulo

O presente trabalho aborda o estudo de correlações entre estrutura e propriedade de uma nova composição de vidros fluorofosfato. O trabalho compreende na síntese e caracterização de vidros fluorofosfatos com a seguinte composição: [80Ba(PO3)2 - 20Al(PO3)3]1-x[80BaF2 - 20AlF3]x(0 ≤ x ≤ 40 - mol%).Ressonância Magnética Nuclear e Espalhamento Raman são técnicas indicadas no estudo estrutural de materiais amorfos, como por exemplo, os vidros. Através dos resultados obtidos por difração de raios-X (DRX) e análise térmica diferencial (DTA) confirmam a formação de um sólido amorfo com concentrações de íons fluoretos de até 30 mol%. No entanto, a partir dos resultados da quantificação dos íons fluoretos via 19F RMN sugerem que houve uma quantidade significativa de perda de fluoreto ou ainda troca dos íons fluoretos por óxidos. Os espectros de 31P e Raman indicam uma gradual conversão das unidades Q2m em Q1m com o aumento de x. 19F RMN indica que os átomos de flúor estão em dois ambientes químicos distintos, onde os íons fluoretos estão ligados com átomos de fósforo ou distribuídos em um ambiente misto de Al/Ba. Resultados obtidos via 19F{31P}-REDOR confirmam a formação da ligação P-F. Os espectros de 27Al mostram a predominância dos átomos de alumínio com geometria octaédrica e ainda os resultados de 27Al{31P}-REDOR sugerem uma coordenação preferencial dos Al com unidades fosfato. Através dos resultados dos acoplamentos dipolares homonucleares via 31P{31P}-DRENAR corroboram com a deconvolução dos espectros de 31P na atribuição das espécies Q1m e Q2m.

In this work was studied the development of structure/property correlations for new fluorophosphate glasses compositions: [80Ba(PO3)2 - 20Al(PO3)3]1-x[80BaF2 - 20AlF3]x(0 ≤ x ≤ 40 - mol%). Most suitable techniques for the structural analysis in case of disordered and amorphous material are Nuclear Magnetic Resonance (NMR) Spectroscopy and Raman scattering. Results from X-ray diffraction (XRD) and differential thermal analysis (DTA) reveal that amorphous samples were obtained for all glass compositions up to x ≤ 30. However, the fluorine quantification via 19F MAS NMR suggests significant fluoride loss and/or fluoride/oxide replacement. Both 31P and Raman results indicate gradual conversion of Q2m units to Q1m units with increasing the fluorine concentration. 19F MAS NMR spectra indicate fluorine atoms in two different chemical environments bonded wither covalently to P-atoms or located in a mixed Al/Ba environment. The P-F assignment is confirmed by 19F{31P}-REDOR experiments. 27Al NMR spectra shows dominantly six-coordinated aluminium, and the 27Al{31P}-REDOR data suggest nearly exclusive coordination of Al with phosphate species. The dipolar coupling constant obtained by 31P{31P}-DRENAR are roughly consistent with 31P spectral deconvolution suggesting the presence of Q1and Q2 species.

Advisors/Committee Members: Eckert, Hellmut.

Subjects/Keywords: Espalhamento Raman de vidro; Fluorophosphate glasses; Nuclear Magnetic Resonance; Raman scattering of glass; Ressonância Magnética Nuclear; Vidros fluorofosfato

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Silva, R. J. M. (2014). Caracterização estrutural de vidros fluorofosfatos utilizando metodologias de RMN. (Masters Thesis). University of São Paulo. Retrieved from http://www.teses.usp.br/teses/disponiveis/76/76132/tde-11082014-141413/ ;

Chicago Manual of Style (16th Edition):

Silva, Raphaell Júnnio Moreira. “Caracterização estrutural de vidros fluorofosfatos utilizando metodologias de RMN.” 2014. Masters Thesis, University of São Paulo. Accessed October 20, 2019. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-11082014-141413/ ;.

MLA Handbook (7th Edition):

Silva, Raphaell Júnnio Moreira. “Caracterização estrutural de vidros fluorofosfatos utilizando metodologias de RMN.” 2014. Web. 20 Oct 2019.

Vancouver:

Silva RJM. Caracterização estrutural de vidros fluorofosfatos utilizando metodologias de RMN. [Internet] [Masters thesis]. University of São Paulo; 2014. [cited 2019 Oct 20]. Available from: http://www.teses.usp.br/teses/disponiveis/76/76132/tde-11082014-141413/ ;.

Council of Science Editors:

Silva RJM. Caracterização estrutural de vidros fluorofosfatos utilizando metodologias de RMN. [Masters Thesis]. University of São Paulo; 2014. Available from: http://www.teses.usp.br/teses/disponiveis/76/76132/tde-11082014-141413/ ;

3. Morrell, Brian. Optical characterization of samarium-doped fluorophosphate glass for x-ray dosimetry for microbeam radiation therapy at the Canadian Light Source.

Degree: 2012, University of Saskatchewan

Microbeam Radiation Therapy (MRT) is an experimental form of radiation treatment which has the potential to improve the treatment of many types of cancer. In MRT, the radiation is applied as a grid by passing the collimated X-ray beam from a synchrotron through a microplane collimator, which is a stack of parallel plates of two materials with dramatically different X-ray transparencies. The peak-to-valley dose ratio (PVDR) is the difference between the dose in the microbeams and the dose delivered between the beams. It is the PVDR that is of biological importance in MRT. Therefore a dosimeter for MRT requires a combination of a large dynamic range for dose response into the kilo-Gray regime, and high spatial resolution on the micron scale. This project characterizes fluorophosphate glasses doped with trivalent samarium ions as a potential valency conversion dosimeter for MRT using the conversion of Sm3+→Sm2+ to measure the delivered dose. Samples irradiated at the Canadian Light Source synchrotron showed X-ray induced conversion that could be optically characterized by changes in the photoluminescence emission spectra to obtain irradiation dose. The conversion efficiency depends almost linearly on the irradiation dose up to 150 Gy and saturates at doses exceeding 1500 Gy. The conversion shows a strong correlation with an observed increase in absorbance of the glass in the range of 200-750 nm. The absorbance increases with X-ray dose and is related to the formation of phosphorous-oxygen hole centers (POHC) and POn electron centers. The presence of these defects within the irradiated glass was determined by examination of the induced optical absorbance and electron paramagnetic resonance (EPR) spectra. The formation of these hole centers along with the conversion of Sm3+→Sm2+ under X-ray irradiation suggests that the X-rays cause the formation of electron-hole pairs in the glass. The electrons are then primarily captured by the Sm3+ ions, becoming Sm2+ ions, with some of the electrons being captured by POn electron centers. The holes are captured by the POHCs. This process can be represented chemically as Sm3+ + e-→ Sm2+ and PO + h+→POHC. The stability of the Sm conversion under illumination was examined using photoluminescence spectra and the stability of the X-ray induced defects was examined via the induced optical absorbance and EPR spectra. Advisors/Committee Members: Kasap, Safa O., Chapman, Dean, Yang, Qiaoqin, Odeshi, Akindele G., Bourassa, Adam.

Subjects/Keywords: dosimetry; fluorophosphate glass; radiation therapy; photoluminescence; samarium; valence conversion

…conversion is Sm3+ →Sm2+ in a fluorophosphate (FP) glass host exposed to hard X-rays… …emission peaks for Sm3+ and Sm2+ ions embedded in a glass host… …SiO2 glass showing the conversion of Sm3+ → Sm2+ . The atomic transitions that give rise to… …the pattern formed in a Sm3+ -doped sodium borate glass using a femto-second pulsed laser… …Photoluminescence images of Sm3+ -doped glass demonstrating erasure and reconversion of Sm3+ → Sm2+ . The… 

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Morrell, B. (2012). Optical characterization of samarium-doped fluorophosphate glass for x-ray dosimetry for microbeam radiation therapy at the Canadian Light Source. (Thesis). University of Saskatchewan. Retrieved from http://hdl.handle.net/10388/ETD-2012-06-486

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Morrell, Brian. “Optical characterization of samarium-doped fluorophosphate glass for x-ray dosimetry for microbeam radiation therapy at the Canadian Light Source.” 2012. Thesis, University of Saskatchewan. Accessed October 20, 2019. http://hdl.handle.net/10388/ETD-2012-06-486.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Morrell, Brian. “Optical characterization of samarium-doped fluorophosphate glass for x-ray dosimetry for microbeam radiation therapy at the Canadian Light Source.” 2012. Web. 20 Oct 2019.

Vancouver:

Morrell B. Optical characterization of samarium-doped fluorophosphate glass for x-ray dosimetry for microbeam radiation therapy at the Canadian Light Source. [Internet] [Thesis]. University of Saskatchewan; 2012. [cited 2019 Oct 20]. Available from: http://hdl.handle.net/10388/ETD-2012-06-486.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Morrell B. Optical characterization of samarium-doped fluorophosphate glass for x-ray dosimetry for microbeam radiation therapy at the Canadian Light Source. [Thesis]. University of Saskatchewan; 2012. Available from: http://hdl.handle.net/10388/ETD-2012-06-486

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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